Link Elasticsearch indexing progress to elastic_commit_indexer

What does this MR do?

This was previously linking to elastic_full_index. Looking at the size of the elastic_full_index queue is much less valuable considering it is ultimately just spinning up a bunch of elastic_commit_indexer jobs which do all the heavy lifting and it's very likely the elastic_full_index queue is drained in seconds (since there is no back pressure) while the elastic_commit_indexer queue takes days to finish draining.

There are also other queues at play which are indexing non-code documents (eg. issues) but from experience these are drained quicker than the elastic_commit_indexer queue when indexing projects so if we had to pick one queue then elastic_commit_indexer is the best one to show.

We could consider something more sophisticated in future but I wanted to correct this for now since the elastic_full_index queue is not a useful way to track progress.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team