[clang] [Clang] `constexpr` builtin floating point classification / comparison functions (PR #94118)

[Mital Ashok via cfe-commits]

MitalAshok wrote:

@tbaederr Thanks for fixing the build bots. The leak appears to be unrelated to these changes and happen on this line:

https://github.com/llvm/llvm-project/blob/71801707e33c235656b172fa7dfb8662473a95c2/clang/test/Sema/constant-builtins-2.c#L309

It even happens with:

```c
int x = ((unsigned __int128)0) + __builtin_clzg(0u); // expected-error {{not a compile-time constant}}
```

Is there a different file that these tests should be added for? Like AST/ByteCode/builtin-functions.cpp?

https://github.com/llvm/llvm-project/pull/94118