Fixed #22588 -- Fix RegexValidator __eq__

Compare parameters instead of re.pattern instances, and add the other
parameters to the comparison. Also add a __ne__ to make assertNotEqual
work properly.
Fixed #22563: Ignore AUTH_USER_MODEL errors in from_state
Fixed #22325: Ignore __first__ dependencies to your own app
Tests for #22325
Fixed #22606 -- Locmemcache has_key() failed for infinite cache expiry

Refactored cache expiry logic for Locmemcache to make consistent across
all places where accessed, and correctly handle None as expiry time.
Used more precise assertions in cache tests