Switch to `*f32`, `*f64` names for libm

[tgross35]

We should use the C23 names which are more obvious and accurate (double is not always f64). We can leave the */*f symbols for the current version as wrappers but mark them deprecated.

From compiler-builtins, we should be able to export both so LLVM can use either (same as glibc does)

[hulxv]

I want to work on this. Can I be assigned? Is it available to contribute?

[tgross35]

Sure! Assigned.

This should probably look like one commit changing all the names in libm/ and libm-test (perhaps a few other places), then a second adding re-exports. Don't deprecate anything for now, we'll do that later.