Elasticsearch: Intelligently retry bulk-insert failures when indexing database content

What does this MR do?

For database importing, retry individual failed database entry first. If retry is still unsuccessful, schedule another indexing for the particular project instead.

Part of #12372 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.