Switch to new collaborators component (#1405)

Followup to https://github.com/tldraw/brivate/pull/1584

- Removes the old collaborators component, replacing with the new one.
- Removes the associated debug flag

### Change Type

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- [ ] `patch` — Bug Fix
- [ ] `minor` — New Feature
- [x] `major` — Breaking Change
- [ ] `dependencies` — Dependency Update (publishes a `patch` release,
for devDependencies use `internal`)
- [ ] `documentation` — Changes to the documentation only (will not
publish a new version)
- [ ] `tests` — Changes to any testing-related code only (will not
publish a new version)
- [ ] `internal` — Any other changes that don't affect the published
package (will not publish a new version)

### Test Plan

Check that multiplayer presence UI renders correctly

- cursors
- cursor hints (when a peer's cursor goes off the screen)
- selection brush box
- selection/erasing brush
- selected shape(s) outline

### Release Notes

- [Breaking] Removes the old version of LiveCollaborators, replacing it
with the new one based on `TLInstancePresence`

packages/editor/src/lib/utils/debug-flags.ts

@@ -23,7 +23,6 @@ export const debugFlags = {
 	peopleMenu: createDebugValue('tldrawPeopleMenu', false),
 	logMessages: createDebugValue('tldrawUiLog', []),
 	resetConnectionEveryPing: createDebugValue('tldrawResetConnectionEveryPing', false),
-	newLiveCollaborators: createDebugValue('tldrawNewLiveCollaborators', false),
 }
 
 declare global {