[libc] [llvm] [libc][math] Refactor cbrt implementation to header-only in src/__support/math folder. (PR #151837)

[Muhammad Bassiouni via llvm-commits]

bassiounix wrote:

### Merge activity

* **Aug 3, 5:52 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/151837).


https://github.com/llvm/llvm-project/pull/151837