[analyzer] Support allocClassWithName in OSObjectCStyleCast checker

`allocClassWithName` allocates an object with the given type.
The type is actually provided as a string argument (type's name).
This creates a possibility for not particularly useful warnings
from the analyzer.

In order to combat with those, this patch checks for casts of the
`allocClassWithName` results to types mentioned directly as its
argument.  All other uses of this method should be reasoned about
as before.

rdar://72165694

Differential Revision: https://reviews.llvm.org/D99500