[WIP] Add Epics select dropdown to Issue sidebar
What does this MR do?
Adds Epics select dropdown with searching support to Issue sidebar.
Does this MR meet the acceptance criteria?
- Changelog entry
- Documentation created/updated or follow-up review issue created
- Code review guidelines
- Merge request performance guidelines
- Style guides
- Separation of EE specific content
- Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
- Tested in all supported browsers