Update internal branch list API calls to use new keyset pagination

This is a follow up issue that came out of #208738 (closed). We've implemented using gitaly's native pagination, but we need to start using this internally first before we release it to the public and deprecate the old pagination.

Related MRs:

• !37524 (merged)
• !35819 (merged)

We need to go through the existing calls of Branch List API from our frontend to use new keyset pagination. This is one of such examples, but there could be more. We need to start using this to realise the performance gain we're after.

• spec/frontend/ref/components/ref_selector_spec.js