[alpha.webkit.UncountedLocalVarsChecker] Allow uncounted object references...

[alpha.webkit.UncountedLocalVarsChecker] Allow uncounted object references within trivial statements (#82229)

This PR makes alpha.webkit.UncountedLocalVarsChecker ignore raw
references and pointers to a ref counted type which appears within
"trival" statements. To do this, this PR extends TrivialFunctionAnalysis
so that it can also analyze "triviality" of statements as well as that
of functions Each Visit* function is now augmented with
withCachedResult, which is responsible for looking up and updating the
cache for each Visit* functions.

As this PR dramatically improves the false positive rate of the checker,
it also deletes the code to ignore raw pointers and references within if
and for statements.