PR Declutter

[JStuve]

Is your feature request related to a problem? Please describe.
When working on a PR and wanted feedback on a bigger design it can something turn into a long feed of conversation, making it feel cluttered.

Describe the solution you'd like
It would be nice to hide the clutter from a PR so that I can view only the open conversations.

Requirements

• Manually hide/unhide timeline elements so that it takes up the smallest space possible
• Toggle button
  • Show all: Current behavior
  • Show active: Any review that is open and non-manually hidden timeline elements will be visible
  • Show Review Only: Any open review timeline element only