State: Batch updates to title (and other post properties) for undo

[aduth]

Closes #4057
Related: #4956

This pull request seeks to apply the same undo buffering introduced in #4956 for blocks to apply to all post property updates. This particularly impacts the post title, where the changes proposed here will improve undo to apply to aggregate of the changes applied to the title, rather than a single character at a time.

In the process, the KeyboardShortcuts component has been updated to accept children to which keyboard events should be monitored. This was proposed as a future enhancement in the original implementation (#1944).

Due to issues with React controlled textareas (facebook/react#8514), key events for undo/redo must be monitored manually within the title, and redirected as dispatching actions to the editor store.

Testing instructions:

Verify that when entering a title, pressing Undo no longer reverts one character at a time, but rather all changes made in sequence.

This same behavior applies to any other post property change (e.g. status, author, etc).