Optimize parameter resolution by avoiding redundant calls to _resolve_parameters_ if _is_parameterized_ is False

[tanujkhattar]

Summarize the task
cirq.resolve_parameters protocol delegates to the _resolve_parameters_ method of the value for which we need to resolve parameters of. However, this should happen only if the value is parameterized in the first place, to avoid doing redundant work trying to resolve parameters (by creating unnecessary copies for example ).

Acceptance criteria - when is the task considered done?
As part of making parameter resolution more performant, we should:

1. Check that we should call value._resolve_parameters_() only if value._is_parameterized_() returns True.
2. Cache the results of _is_parameterized_ for FrozenCircuit and Moment because they are immutable objects.

[maffoo]

Gate and Operation should be immutable too. would be good to cache _is_parameterized_ for them as well. Might have to do this on subclass at a time for gates.

[zchen088]

To be specific, I think we're talking about adding @_compat.cached_method to invocations of _is_parameterized_. If this sounds good, I could maybe try doing this (though it's been a while since I've had a Cirq dev environment spun up).

[tanujkhattar]

@zchen088 That's correct, we should be using @_compat.cached_method to make sure we include self in the cache.