[clang] add: NUMERIC_TYPE_SWITCH (PR #161755)

[Aditya Chaudhari via cfe-commits]

AdityaC4 wrote:

@tbaederr Thanks for the context. Since `Floating` still needs an explicit `allocFloat` while `pushInteger` already handles the `IntAP`/`IntAPS` allocations, maybe we should drop the new `NUMERIC_TYPE_SWITCH`. If not we could add a helper that checks `needsAlloc<T>()` and `singleWord()` so the float path auto-allocates when needed, which would let us make a unified switch.

https://github.com/llvm/llvm-project/pull/161755