Canonicalize Not(...) more aggressively in deadness analysis

This change makes deadness analysis canonicalize Not expressions more
aggressively using DeMorgan's law.  It uses this added power to more
aggressively detect And and Or expressions whose operands include a predicate
and its negation.

The main motivation for doing this is to simplify ~#true to #false and ~#false
to #true, but I can't test that directly before another related change lands.

PiperOrigin-RevId: 230356857