Merge the remainder of the "experimental" branch

Summary:
Depends on D20986. Ref T13395. This mostly collapses the entire "experimental" branch into "master".

I plan to change the "Ref/Hardpoint" pattern to become future oriented, but this is more steps forward than sideways.

Test Plan: Ran various arc workflows.

Maniphest Tasks: T13395

Differential Revision: https://secure.phabricator.com/D20987