Tracking issue: build a better references panel

Created by: mrnugget

Goal

Create a better code intelligence panel to display definition, references, implemenations.

Turn the reference panel into a serious tool that doesn't make users fall back to their editor/IDE.

Problems with current panel

• There are some general UX problems with the panel due to how it is integrated in our Sourcegraph web app and how it loads data: https://github.com/sourcegraph/sourcegraph/issues/30022
• It doesn't stay open when navigating through references: https://github.com/sourcegraph/sourcegraph/issues/13722
• It's not possible to filter references: https://github.com/sourcegraph/sourcegraph/issues/28480
• It's not possible to exclude file types
• Navigating through references is incredibly slow
• It's not possible to scroll through full list of references quickly (you need to load, scroll, load some more, scroll, load some more, scroll, load some more)

Plan

• Stage 1: build a proof-of-concept and get internal feedback

  • https://github.com/sourcegraph/sourcegraph/issues/30969
    • https://github.com/sourcegraph/sourcegraph/pull/30095

• MERGE and start INTERNAL user testing

• Stage 2 (👈 WE ARE HERE): fix known bugs and deficits in proof-of-concept

  • #30974 (closed)
  • #30971 (closed)
  • #31640 (closed)
  • #31641 (closed)
  • #31642 (closed)
  • #30970 (closed)
    • #31645 (closed)
  • #32307 (closed)
  • #32328 (closed)
  • https://github.com/sourcegraph/sourcegraph/issues/33412
  • https://github.com/sourcegraph/sourcegraph/issues/33418

• Stage 3: Discuss with Growth & Integrations that we will need features X, Y, Z in order to keep using extension API in SPA

• Stage 4: Ship a better panel to all users

  • #30972
  • #30973
  • https://github.com/sourcegraph/sourcegraph/issues/33417