Security Configuration: Add modal for searching and adding refs to be tracked

Summary

When adding a ref to be tracked for vulnerability scanning, we need to add UI that allows to search and select refs:

Note: Inspired by the "Find file UI"

Implementation plan

• Add modal that opens when "Track new refs" button is clicked
• Fetch most recent refs
• Add ref-list with checkbox-toggle
• Add functionality to select refs to be tracked
• Add Banner that keeps track of the count (existing + plus new)
• Add logic to warn the user when the maximum count is reached
• Add search functionality (TODO: Need to investigate if there is already a GraphQL endpoint for this)
• Add functionality to expand the refs that are to be added
• Call mutation to track selected refs once the user has finished with the process

References

• Design: #460889[Add_new_ref_-_filter__search__select.png]