[libc] Provide compiler version properties (#73344)

This will be used to support conditional compilation based on compiler
version.
We adopt the same convention as
[libc++](https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config)
- thx @legrosbuffle for the suggestion!
Usage:
```
#if defined(LIBC_COMPILER_CLANG_VER)
#  if LIBC_COMPILER_CLANG_VER < 1500
#    warning "Libc only supports Clang 15 and later"
#  endif
#elif defined(LIBC_COMPILER_GCC_VER)
#  if LIBC_COMPILER_GCC_VER < 1500
#    warning "Libc only supports GCC 15 and later"
#  endif
#elif defined(LIBC_COMPILER_MSC_VER)
#  if LIBC_COMPILER_MSC_VER < 1930
#    warning "Libc only supports Visual Studio 2022 RTW (17.0) and later"
#  endif
#endif
```