[flang] [llvm] [Flang][OpenMP] Add parser support for grainsize and num_tasks clause (PR #113136)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `flang,llvm` at step 2 "checkout".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/9550

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 2 (checkout) failure: update (failure)
git version 2.35.3
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': Could not resolve host: github.com
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': Could not resolve host: github.com

```

</details>

https://github.com/llvm/llvm-project/pull/113136