Merge changes from topic "test_metadata_cp-udc-mainline-prod" into udc-mainline-prod

* changes:
  Use result.Config.PrebuiltOS() to get prebuiltHost in test_spec_test
  Add test for soong/testing/test_spec.
  Set testModule to true in cc.NewTest().
  Add Singleton class to collect and validate test spec metadata.
  Add test spec provider to test modules.
  Add proto for Test ownership metadata.