Add a new `test_options.tags` attribute to customize test execution

The `test_options.tags` attribute provides additional metadata to
customize test execution by downstream test runners. The tags have no
special meaning to Soong.

Bug: 240928948
Test: manually add `test_options.tags` attribute and run:
    $ refreshmod && \
      cat out/target/product/generic/module-info.json |\
      grep <tags>
Change-Id: I35267f6608e48c6184e56530ef128d93b2f97522