Clang's AST builder uses the `getPropertyAttributesAsWritten()` method
that contains the bitmasks of only the attributes present in the source,
and not the default attributes that are present in
`getPropertyAttributes()`. This method was relevant in the past when two
separate enums existed for Objective-C property attributes, and had to
be updated whenever new property attributes were introduced. As of this
commit, nullability attributes are not present when written due to the
method not containing the bitmask comparison for the `nullable` and
`null_resettable` attributes.
9721fbf85b83c1cb67cea542c5558f99a07766cf consolidated the two property
attribute enums into a single
enum. With this change, the AST can directly store the written
attributes without having to construct the bitmask again. This commit
removes the `getPropertyAttributesAsWritten()` method and updates the
AST to directly store the written attributes instead.
rdar://131053727
85eb10e270