Summary:
This one wasn't quite so trivial as `@pixie-labs/api-react`, but still pretty straightforward:
- Moves the source files over to `@pixie-labs/ui`
- Deletes no-longer-applicable support files
- Updates import paths everywhere
- Updates scripts for regenerating GQL schema and TS protos
- Removes all references to the package's former existence
- Re-runs Yarn (yes, more lock updates)
This diff only moves the code back and fixes its usage; it doesn't touch PC-981 or PC-982.

Test Plan: Smoke test. Run unit tests. Don't forget you'll need to re-run `yarn install && yarn build_deps` on this one since an entire package ceased to exist.

Reviewers: michelle, vihang, philkuz, #third_party_approvers

Reviewed By: vihang, #third_party_approvers

JIRA Issues: PC-979, PC-980

Differential Revision: https://phab.corp.pixielabs.ai/D8873

GitOrigin-RevId: 2de4793932939ece01655d77f5f6a3a904ebb61b