[clang-tools-extra] [clang-tidy] Add portability-avoid-platform-specific-fundamental-types (PR #146970)

[JJ Marr via cfe-commits]

jj-marr wrote:

@vbvictor It makes sense to provide an autofix for `float`/`double`, since I have never heard of them being anything other than IEEE754 32-bit binary floats or IEEE754 64-bit binary floats respectively.

`char8_t` will always be `unsigned char` so a fix from `unsigned char` to `char8_t` could make sense as well.

Is an autofix from `char` or `signed char` to `char8_t` is a good idea?

https://github.com/llvm/llvm-project/pull/146970