Arm backend: Add support for fill_.Scalar

[oscarandersson8218]

Adds support for fill_.Scalar. fill_.scalar is decomposed to full_like which is already supported by Arm backend.

cc @digantdesai @freddan80 @per @zingo

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/14501

• 📄 Preview Python docs built from this PR

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

❌ 3 New Failures, 2 Cancelled Jobs

As of commit 665b117 with merge base 7e228ee ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t b78316ae7b29bf36350303e40659c79a989c56a2a7448f4e6cca79e37fc45c40 /exec failed with exit code 1
• trunk / test-arm-ootb-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 7f01a8801cc9bf0e6b599416bb3bbfdcd96a70656f4b071cc24119719bbbdc6e /exec failed with exit code 1
• trunk / test-llama-runner-mac (fp32, coreml) / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• Check Labels (gh)
• periodic (gh)

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