[libc][math][c23] Add rsqrtf() function (#159615)
Closes #159614
**Changes:**
- Initial implementation of rsqrt for single precision float
**Some small unrelated style changes to this PR (that I missed in my
rsqrtf16 PR):**
- Added extra - to the top comments to make it look nicer in
libc/shared/math/rsqrtf16.h
- Put rsqrtf16 inside of libc/src/__support/math/CMakeLists.txt in
sorted order
- Rearanged libc_math_function rsqrtf16 in Bazel to match alphabetical
order
