distinguish overflow and unimplemented in Step::steps_between

[michirakara]

This PR implemented enhancement of Step::steps_between in #48117 , with hint-like return type, returning (usize, Option<usize>).

When &a <= &b and steps between a and b is less than or equal to usize::MAX, steps_between(&a, &b) == (n, Some(n)).

When &a <= &b and steps between a and b is greater than usize::MAX, steps_between(&a, &b) == (usize::MAX, None).

When &a > &b , steps_between(&a, &b) == (0, None).

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @joboet (or someone else) some time within the next two weeks.

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[rust-log-analyzer]

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

   Compiling llvm-bitcode-linker v0.0.1 (/checkout/src/tools/llvm-bitcode-linker)
    Finished `release` profile [optimized] target(s) in 5.92s
##[endgroup]
##[group]Building stage1 library artifacts (x86_64-unknown-linux-gnu)
error: process didn't exit successfully: `/checkout/obj/build/bootstrap/debug/rustc /checkout/obj/build/bootstrap/debug/rustc -vV` (exit status: 254)
error: rustc interrupted by SIGSEGV, printing backtrace


/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(+0xb500c3)[0x7f7bd73820c3]
/lib/x86_64-linux-gnu/libc.so.6(+0x42520)[0x7f7bd64e1520]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(+0xb97590)[0x7f7bd73c9590]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(+0xab6501)[0x7f7bd72e8501]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(_RNvCskxAl5tAjtnG_17rustc_driver_impl14handle_options+0xf7)[0x7f7bd73693d7]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(+0xb2c12e)[0x7f7bd735e12e]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/librustc_driver-a1b8689b027a25d5.so(_RNvCskxAl5tAjtnG_17rustc_driver_impl4main+0x30e)[0x7f7bd736b64e]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc(+0x1167)[0x55ea71829167]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc(+0x1133)[0x55ea71829133]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc(+0x1149)[0x55ea71829149]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/lib/libstd-0c7268aa146b0081.so(_RNvNtCsaxe4SnUHES6_3std2rt19lang_start_internal+0x4af)[0x7f7bd674440f]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc(+0x1198)[0x55ea71829198]
/lib/x86_64-linux-gnu/libc.so.6(+0x29d90)[0x7f7bd64c8d90]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80)[0x7f7bd64c8e40]
/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc(+0x1065)[0x55ea71829065]
note: we would appreciate a report at https://github.com/rust-lang/rust
help: you can increase rustc's stack size by setting RUST_MIN_STACK=16777216
help: you can increase rustc's stack size by setting RUST_MIN_STACK=16777216
rustc exited with signal: 11 (SIGSEGV) (core dumped)
Build completed unsuccessfully in 0:05:02
  local time: Thu Sep 26 02:45:41 UTC 2024
  network time: Thu, 26 Sep 2024 02:45:41 GMT
##[error]Process completed with exit code 1.

[joboet]

r? libs-api