Internal: b/226976190

The time has come again. :)
These are the next batch of deprecations that have expired.

This one is a bit more significant than last batches, so it may take some time to get everyone migrated.
This should only be closed after the final migration guide for this batch lands in the website repo.

Notes

• See comments below from @rydmike, as the button clean up is done, there are a lot of documentation improvements that should be made at the same time