Create new end-to-end test for Commit index

Each of our indices is end-to-end tested here https://gitlab.com/gitlab-org/gitlab/-/tree/master/qa/qa/specs/features/ee/api/9_enablement/elasticsearch/index_tests

To maintain end-to-end test parity with other indices we'll need to add a simple commit search test to the suite.

Steps

• Verify the timeout intervals will work with commits https://gitlab.com/gitlab-org/gitlab/-/blob/6d48b219079270aab8de5b97f7a9928ca2fda898/qa/qa/runtime/search.rb#L11-L13
• Create the Commits Index test ruby file. Similar to Notes In the Index test Directory

MR Example: !66986 (merged)