Tracking issue: Rethinking RedrawRequested

[goddessfreya]

This issue tracks the implementation of the RedrawRequested API changes that were discussed in #1041. PRs implementing this change should be made against the redraw-requested-2.0 branch, and we'll merge that branch onto master once it's implemented on all platforms.

• Public API changed
• Implemented on all platforms
  • Windows - Implement revamped RedrawRequested on Windows #1050
  • macOS - Implement revamped RedrawRequested on macOS #1235
  • iOS - Implement revamped RedrawRequested on iOS. #1299
  • Linux X11 - Implement changes to RedrawRequested event #1062
  • Linux Wayland - Implemented revamped RedrawRequested for linux wayland #1237
  • Web - Implement revamped RedrawRequested on Web #1301
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated feature matrix, if new features were added or implemented.

[mtak-]

#1133 gets iOS 90% of the way there. There will need to be a separate (trivial) pr to actually send out the events.