Add feature flag for index circuit breakers

What does this MR do and why?

Add feature flag for zoekt index circuit breakers

Until we have index level eviction logic, we don't want to skip indexing when an index watermark is exceeded.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

added groupglobal search label

assigned to @johnmason

added devopsdata stores sectioncore platform labels

Proper labels assigned to this merge request. Please ignore me.

@johnmason - please see the following guidance and update this merge request.

	1 Error
	Please add typebug typefeature, or typemaintenance label to this merge request.

added docs-only label

added 1 commit

• bf660d13 - Add feature flag for zoekt index circuit breakers

Compare with previous version

marked this merge request as ready

changed the description

added maintenancescalability label

added typemaintenance label

resolved all threads

resolved all threads

removed docs-only label

@rkumar555 can you do initial review here?

requested review from @rkumar555

added backend feature flag labels

Reviewer roulette

Category	Reviewer	Maintainer
backend	@tigerwnz (UTC+11, 15 hours ahead of author)	@pskorupa (UTC+2, 6 hours ahead of author)

Please refer to documentation page for guidance on how you can benefit from the Reviewer Roulette, or use the GitLab Review Workload Dashboard to find other available reviewers.

If needed, you can retry the danger-review job that generated this comment.

Generated by Danger

@johnmason Looks good to me. Just one question, should we add some expectation in the test when FF zoekt_index_circuit_breaker is true?

approved this merge request

@terrichu Could you please do the maintainer review?