[MPS] Update MPS documentation; add helper script to build mps_executor_runner

[DenisVieriu97]

Summary of changes:

• Update MPS documentation to reflect all changes since previous release
• Add helper script to build mps_executor_runner

Testing:

• Verified that mps_executor_runner builds correctly:

./examples/apple/mps/scripts/build_mps_executor_runner.sh
/examples/apple/mps/scripts/build_mps_executor_runner.sh --Debug

Verified that the docs are building correctly:

cd docs
make html

cc @shoumikhin, @cccclai

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/3329

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 2 New Failures

As of commit cfefe29 with merge base d3326a2 ():

NEW FAILURES - The following jobs have failed:

• Apple / test-demo-ios / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 1
• Apple / upload-frameworks-ios (gh)
  Credentials could not be loaded, please check your action inputs: Could not load credentials from any providers

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[DenisVieriu97]

❌ 1 New Failure, 2 Pending

As of commit cfefe29 with merge base d3326a2 (image):

NEW FAILURE - The following job has failed:
Apple / test-demo-ios / macos-job (gh)
RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 1
This comment was automatically generated by Dr. CI and updates every 15 minutes.

This failed because it didn't have the changes from: #3327.
That one just got merged and it fixes this issue (test-ios-mps passes there).