Document Quantizer API and precision options for MTK backend

[cccclai]

Added Quantizer API section with precision configuration example.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15091

• 📄 Preview Python docs built from this PR

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

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

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

✅ You can merge normally! (2 Unrelated Failures)

As of commit 07e677e with merge base ae1f3ed ():

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

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

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.

[cccclai]

@pytorchbot cherry-pick --onto release/1.0 -c docs

[pytorchbot]

Cherry picking #15091

The cherry pick PR is at #15203 The following tracker issues are updated:

• [v1.0.0] Release Tracker #14288 (comment)

Details for Dev Infra team

Raised by workflow job