Fix the diff visualizer of connected sessions

[boatbomber]

Clicking on the "X changes X ago" message opens up a handy diff visualizer to see what those changes were. However, it had quite a few issues that needed fixing.

• Disconnecting a session with it expanded caused an error as it tried to read the serveSession that no longer exists during the page fade transition. (Disconnecting with synced changes expanded breaks the plugin #671)
  • Resolved by converting to stateful component and holding the serveSession during the lifetime to ensure it can render the last known changes during the fade transition
• Leaving it open while new changes are synced did not update the visualizer
  • The patch data was piggybacking on an existing binding, which meant that new patches did not trigger rerender.
    • Resolved by converting to state
    • Also made some improvements to that old binding
      • Moved from app to connected page for better organization and separation of duties
      • No more useless updates causing rerenders with no real change
  • Scroll window child component wouldn't actually display the updated visuals
    • Resolved by making major improvements to VirtualScroller
      • Made more robust against edge case states
      • Made smarter about knowing when it needs to refresh

As you can see in this slow motion GIF, it works now.

[boatbomber]

Whoops, somehow the serveSession is never getting stopped correctly and it continues listening on the port. A memory leak is one thing, but this one is weird.

Edit: Actually, this issue occurs even on master and is unrelated to this PR.