Introduce ktfmt for kotlin files under executorch_android

[phaiting]

Summary

The google-jave-format doesn't work for kotlin file, this diff introduced the standard kotlin format - ktfmt.

run $./gradlew spotlessCheck to see the format issues
run $./gradlew spotlessApply to apply the kotlin format.

Test plan

run via CI jobs

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15094

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❗ 1 Active SEVs

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• [ROCm][CI] Machines under the label linux.rocm.gpu.2 are undergoing maintenance.

❌ 1 New Failure, 2 Unrelated Failures

As of commit 57ea0f7 with merge base dbd0e9f ():

NEW FAILURE - The following job has failed:

• Lint / android-java-format / linux-job (gh)
  RuntimeError: Command docker exec -t b686c705cd2db0b6683f6652f19f5b264aefb4dd93d674388850f258d8da7004 /exec failed with exit code 1

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  runtime/test/test_runtime_etdump_gen.py::RuntimeETDumpGenTest::test_etdump_params_with_bytes_and_buffer
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  runtime/test/test_runtime_etdump_gen.py::RuntimeETDumpGenTest::test_etdump_params_with_bytes_and_buffer

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[phaiting]

@pytorchbot label "release notes: none"

[mergennachin]

where is the CI job configured?