{CI} Change Verify Ref Docs from full test to incremental test

[wangzelin007]

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Change Verify Ref Docs from full test to incremental test:

1. Detect which extensions are involved in the PR code.
2. Only run ref doc tests for related extensions

This checklist is used to make sure that common guidelines for a pull request are followed.

Related command

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your pull request is merged into main branch, a new pull request will be created to update src/index.json automatically.
You only need to update the version information in file setup.py and historical information in file HISTORY.rst in your PR but do not modify src/index.json.

[azure-client-tools-bot-prd]

️✔️Azure CLI Extensions Breaking Change Test

️✔️Non Breaking Changes

[azure-client-tools-bot-prd]

Hi @wangzelin007,
Please write the description of changes which can be perceived by customers into HISTORY.rst.
If you want to release a new extension version, please update the version in setup.py as well.

[azure-client-tools-bot-prd]

Hi @wangzelin007,
Since the current milestone time is less than 7 days, this pr will be reviewed in the next milestone.

[yonzhan]

CI

[bebound]

If the extension is not in the repo, updating index.json will not add it in MODIFIED_EXTS

[wangzelin007]

Maybe we should mark this test as continueOnError, all extensions are independent of each other, we should not let an issue with one extension block other extensions.