Initialize update queue object on mount (#17560)

* Refactor Update Queues to Fix Rebasing Bug

Fixes a bug related to rebasing updates. Once an update has committed,
it should never un-commit, even if interrupted by a higher priority
update. The fix includes a refactor of how update queues work.

This commit is a combination of two PRs:

- #17483 by @sebmarkbage refactors the hook update queue
- #17510 by @acdlite refactors the class and root update queue

Landing one without the other would cause state updates to sometimes be
inconsistent across components, so I've combined them into a single
commit in case they need to be reverted.

Co-authored-by: Sebastian Markbåge <[email protected]>
Co-authored-by: Andrew Clark <[email protected]>

* Initialize update queue object on mount

Instead of lazily initializing update queue objects on the first update,
class and host root queues are created on mount. This simplifies the
logic for appending new updates and matches what we do for hooks.