swift234

SILGen: Decouple "should use materializeForSet" from "materializeForSet was synthesized"

We will sometimes emit materializeForSet for resilience, even if
it is not the preferred method for inout accesses of the property
or subscript.

To avoid having SILGen behavior depend on whether Sema synthesized
a materializeForSet or not, add a more precise predicate. The
general idea as I understand it, is that we want to use
materializeForSet if we do not have perfect information about the
implementation of the property or subscript, due to polymorphism
or resilience.