Properties can also be specified in a protocol/overridden by subclasses,
so they should also be classed as "dynamic" in these cases.
Removed receiver USRs when *not* dynamic, since it's not used for
anything in that case and should be equivalent to the container anyway.
Resolves rdar://92882348.
When building the implicit subscript expression, set the "implicit" bit
correctly and pass it through in the indexer so that we get implicit
refernces to the subscript. This would be useful for e.g. searching for
all uses of the dynamic subscript.
Currently includes both the implicit references to the
subscript(dynamicMember:) and the explicit references to the underlying
property/subscript declarations.
rdar://49028783