[libc][math] Refactor floor family to header-only (#182194)

Refactors the floor math family to be header-only.

Closes https://github.com/llvm/llvm-project/issues/182193

Target Functions:
  - floor
  - floorbf16
  - floorf
  - floorf128
  - floorf16
  - floorl

GitOrigin-RevId: fb6b470caedc37c880b5112bd1c85be5f55e9114