(new theory) Update TheoryUF to new interface (#4944)

(new theory) Update TheoryUF to new interface (#4944)

This updates TheoryUF to use the 4 check callbacks instead of implementing check, and uses the official TheoryState object instead of its context::CDO<bool> d_conflict field.

It also makes a minor change to collectModelValues for const and to preNotifyFact to include an isInternal flag.