[libc] [llvm] [libc][math] Refactor atan2f128 implementation to header-only in src/__support/math folder. (PR #151012)

[Muhammad Bassiouni via llvm-commits]

bassiounix wrote:

### Merge activity

* **Aug 1, 9:03 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/151012).


https://github.com/llvm/llvm-project/pull/151012