Specify library name and version:

    - gnu-arm-embedded-toolchain/11.3.0
    - gnu-arm-embedded-toolchain/12.2.0

New addition to ConanCenter.

The author of the toolchain binaries is ARM inc. Original files
can be found here:
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

Makes the bare metal ARM GCC toolchain accessible via "tool_requires"
for bare metal projects.

- Add ARM processor license ID
- Add validation step, raise an exception if the OS & Arch settings are not
  supported
- Define conf_info attributes for CMake Toolchain
- Move toolchain.cmake to test_package
- Remove unnecessary code from toolchain.cmake
- Get test_package to build

- Use build_requirements for test_package

- remove set(CMAKE_SYSTEM_NAME Generic) from test_v1_package
- remove set(CMAKE_SYSTEM_PROCESSOR ARM) from test_v1_package

No reason to not support gcc 11.3.0 for mac when the binaries work for
both x86 and armv8.

Since the compiler doesn't package the license within its archive
files and downloading it is flakey, the license will be placed in the
recipe directory.

Override CMakeToolchain generate in test packages

Because of "Deprecation of support for legacy CMake generators in Conan
Center" conan-io#17406, test_v1_packages are no longer needed, which will
simplify the build and recipe process.

Works on Mac, will see if it can work anywhere else.

There is no reason to allow build profiles targeting compilers outside
of gcc for this gcc package.

The build process downloads the binaries which is necessary if CCI
doesn't save the binaries for compiler which can reach up to 3GB in size
for every architecture and os.

Even though these flags will be and should be used 99% of the time, it
shouldn't be forced on the user.

12.3.0 has license files embedded within the zip file which is an
improvement over all of the previous packages.

Picolibc is a size optimized implementation of stdlibc with additional
features.

I think this is a bad idea because storing all of these binaries takes
up a lot of space on the server.

This will ensure that picolibc.specs was installed into the toolchain
correctly.

- Licenses now use the URLs from the official ARM website
- Remove picolibc integration
    - Will make a separate package for picolibc
- Remove workaround in test_package/CMakeLists.txt by directly
  referencing the toolchain.cmake file
- Remove c++20 setting in test_package
- Add compiler check in the validate method of the test_package not
  the build method
- Overall cleanup some of the recipe
- Cleanup the package directory layout

CI Hooks does not like random directories in the root of the package
directory.

Co-authored-by: Jordan Williams <[email protected]>

Conan's adds host side flags to the conan_toolchain.cmake file which
interferes with arm-none-eabi-g++. To fix this, we set CMAKE_CXX_FLAGS
to an empty string, then provide target specific flags to the
executable.