[Analyzer][WebKit] Use tri-state types for relevant predicates

Some of the predicates can't always be decided - for example when a type
definition isn't available. At the same time it's necessary to let
client code decide what to do about such cases - specifically we can't
just use true or false values as there are callees with
conflicting strategies how to handle this.

This is a speculative fix for PR47276.

Differential Revision: https://reviews.llvm.org/D88133