Handle DefLabel in constrainValue

Reviewed By: @swtaarrs

Differential Revision: D1399894
Casting Resource to Array should give array($resource)

Summary: @kmiller68 fixed this for Object cast, this diff fixes the similar array cast.

Reviewed By: @fredemmott

Differential Revision: D1399347
Fix await/yield operator precedence

Summary: Do not rely on magic, declare operator precedence correctly.

Reviewed By: @elgenie

Differential Revision: D1403498
Handle mismatching fromLoad state in refcount opts

Summary: It can actually be legit to have mismatching fromLoad states, as long as the
realCounts are suitable.  Includes a minimized test case for the case that's
been occasionally killing our flib runs.

Reviewed By: @swtaarrs

Differential Revision: D1404995