fix: Build on stock apple clang.

[charlielye]

Description

As title.

Checklist:

• I have reviewed my diff in github, line by line.
• Every change is related to the PR description.
• The branch has been merged with/rebased against the head of its merge target.
• There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• There are no circuit changes, OR a cryptographer has been assigned for review.
• New functions, classes, etc. have been documented according to the doxygen comment format. Classes and structs must have @brief describing the intended functionality.
• If existing code has been modified, such documentation has been added or updated.
• No superfluous include directives have been added.
• I have linked to any issue(s) it resolves.
• I'm happy for the PR to be merged at the reviewer's next convenience.

[kevaundray]

For context:

Apple Clang version 14.0.0 was not able to compile the current barretenberg due to libc++ not having the methods on std::span that barretenberg were calling. It works on libstdc++ which implies that there is a discrepancy between libstdc++ and libc++ for this feature (understandable because its quite new).

Note: It does work on Apple Clang version 14.0.3.

Snippet of the error:

[49/140] Building CXX object src/barretenberg/polynomials/CMakeFiles/polynomials_objects.dir/polynomial.cpp.o
[157](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:158)
FAILED: src/barretenberg/polynomials/CMakeFiles/polynomials_objects.dir/polynomial.cpp.o 
[158](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:159)
/Applications/Xcode_14.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -DNO_OMP_MULTITHREADING -DNO_TBB -I/Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src -I/Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src/msgpack-c/include -std=gnu++20 -isysroot /Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk -mmacosx-version-min=12.6 -O3 -pthread -Werror -Wall -Wextra -Wconversion -Wsign-conversion -Wfatal-errors -fcolor-diagnostics -fconstexpr-steps=100000000 -MD -MT src/barretenberg/polynomials/CMakeFiles/polynomials_objects.dir/polynomial.cpp.o -MF src/barretenberg/polynomials/CMakeFiles/polynomials_objects.dir/polynomial.cpp.o.d -o src/barretenberg/polynomials/CMakeFiles/polynomials_objects.dir/polynomial.cpp.o -c /Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src/barretenberg/polynomials/polynomial.cpp
[159](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:160)
In file included from /Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src/barretenberg/polynomials/polynomial.cpp:1:
[160](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:161)
/Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src/barretenberg/polynomials/polynomial.hpp:199:88: fatal error: no matching constructor for initialization of 'std::span<field<Bn254FrParams>, 18446744073709551615>' (aka 'std::span<barretenberg::field<barretenberg::Bn254FrParams>, 18446744073709551615>')
[161](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:162)
    void factor_roots(std::span<const Fr> roots) { polynomial_arithmetic::factor_roots(std::span{ *this }, roots); };
[162](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:163)
                                                                                       ^        ~~~~~~~~~
[163](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:164)
/Users/runner/work/bb-test-me-out/bb-test-me-out/cpp/src/barretenberg/polynomials/polynomial.cpp:349:16: note: in instantiation of member function 'barretenberg::Polynomial<barretenberg::field<barretenberg::Bn254FrParams>>::factor_roots' requested here
[164](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:165)
template class Polynomial<barretenberg::fr>;
[165](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:166)
               ^
[166](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:167)
/Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/usr/include/c++/v1/span:402:15: note: candidate constructor not viable: no known conversion from 'barretenberg::Polynomial<barretenberg::fr>' to 'const std::span<barretenberg::field<barretenberg::Bn254FrParams>, 18446744073709551615>' for 1st argument
[167](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:168)
    constexpr span           (const span&) noexcept = default;
[168](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:169)
              ^
[169](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:170)
/Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/usr/include/c++/v1/span:410:15: note: candidate template ignored: could not match 'std::span<barretenberg::field<barretenberg::Bn254FrParams>, 18446744073709551615>::element_type[_Sz]' against 'barretenberg::Polynomial<barretenberg::fr>'
[170](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:171)
    constexpr span(element_type (&__arr)[_Sz])          noexcept : __data{__arr}, __size{_Sz} {}
[171](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:172)
              ^
[172](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:173)
/Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/usr/include/c++/v1/span:415:15: note: candidate template ignored: could not match 'array' against 'Polynomial'
[173](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:174)
    constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
[174](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:175)
              ^
[175](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:176)
/Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/usr/include/c++/v1/span:420:15: note: candidate template ignored: could not match 'array' against 'Polynomial'
[176](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:177)
    constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
[177](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:178)
              ^
[178](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:179)
/Applications/Xcode_14.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/usr/include/c++/v1/span:424:19: note: candidate template ignored: requirement '__is_span_compatible_container<barretenberg::Polynomial<barretenberg::field<barretenberg::Bn254FrParams>>, barretenberg::field<barretenberg::Bn254FrParams>, void>::value' was not satisfied [with _Container = barretenberg::Polynomial<barretenberg::fr>]
[179](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:180)
        constexpr span(      _Container& __c,
[180](https://github.com/crate-crypto/bb-test-me-out/actions/runs/5518686540/jobs/10062978813#step:5:181)
                  ^