Experimental reference panel: add independent pagination for references/implementations

Created by: mrnugget

This fixes #30971 (closed) by adding pagination to "References" and "Implementations" in the experimental reference panel.

Both lists can be independently paginated without re-loading data that was already requested before.

https://user-images.githubusercontent.com/1185253/154961635-44588361-3ee7-4d45-baf6-8a0eda6a627b.mp4

Test plan

• Uploaded LSIF dump for sourcegraph/sourcegraph and opened reference panel on ShareableStore
• Tested this locally (see video above) with firstReferences and firstImplementations set to 10 to easily test the cases where there is
  • no more data
  • more data
  • more data being loaded
• Watched developer tools network tab for requests and inspected those