ExtractAdapters: Support int4 models and external data config

[jambayk]

Describe your changes

• ExtractAdapters pass supports int4 quantized models.
• Previously output models were always saved with external data. External data config options are exposed to the user.
• export_adapters script also supports quantizing the weights to int4.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.
• Is this PR including examples changes? If yes, please remember to update example documentation in a follow-up PR.

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