Test ownership has been used in multiple aspects: default assignee for flaky bugs, default reviewer for PRs to deflake tests, etc, but it happens when people add new tests but miss the ownership info.

We need to create a pre-submit test to enforce the test ownership in TESTOWNERS for each builder defined in .ci.yaml.

• Make sure all existing tests have ownership Add test ownership for firebase tests and docs tests #87145
• Support ownership query from cocoon side Support test ownership validation cocoon#1301
• Create a recipe to check test ownership (recipe)
• Create a pre-submit test to enforce test ownership check (recipe)
• Enable the check in pre-submit Enable test ownership validation test in pre-submit #87310