[clang] [CIR][OpenMP] Implement lowering for the 'num_threads' clause for 'parallel' directive (PR #202466)

[Sergio Afonso via cfe-commits]

skatrak wrote:

@pedropiin could you add a public email address to your GitHub account following the [LLVM developer policy](https://www.llvm.org/docs/DeveloperPolicy.html#github-email-address)? Currently, when we merge your PRs your commits point to a GitHub no-reply address and you don't get notified of potentially related post-merge breakages.

https://github.com/llvm/llvm-project/pull/202466