Add instance security project-selector component

What does this MR do?

This MR adds a component (and a subcomponent) that lets the user search, add and remove projects that should be included in the instance-level security dashboard.

Note: To keep the changes to a minimum, this MR only adds the new components but does not integrate it with the dashboards. (This will happen in a follow-up MR).

Screenshots

instance_lvl_dashboard_project_selector

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.
• Tested in all supported browsers