[MPS] Add portable grid_sampler_2d implementation + tests

[DenisVieriu97]

Upstream grid_sampler_2d (cpu implementation) and the tests implemented by @versi379

Summary of changes:

• Add grid_sampler_2d implementation
• Add tests for grid_sampler_2d tests

cc @cccclai , @shoumikhin

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/10561

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❌ 1 New Failure, 1 Cancelled Job

As of commit 682b539 with merge base c5dd476 ():

NEW FAILURE - The following job has failed:

• pull / android / run-emulator (gh)
  The process '/usr/bin/sh' failed with exit code 255

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / test-static-llama-qnn-linux / linux-job (gh)
  ##[error]The operation was canceled.

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