Add `skip gradle check` that doesn't run gradle checks but passes the `run gradle check` requirement.

[dblock]

Is your feature request related to a problem? Please describe.

We often make PRs such as #812 that are a README change or similar trivialities. This wastes a costly and time-consuming run gradle check.

Describe the solution you'd like

Admins should be able to comment run gradle check or skip gradle check which will respectively run or skip gradle check and satisfy the gradle check requirement. It should also be clear which one was chosen when looking at a PR.

Describe alternatives you've considered

Just always run gradle checks. In that case I'd want to be able to [skip gradle check] in the commit message.

Additional context

Related to https://github.com/opensearch-project/OpenSearch/issues/597

[andrross]

Closing now that #13498 is implemented