This PR makes finding class declarations properties in decorators are
applied to more generic to all properties that may be in a decorator,
and adds helper methods enabling getting the property assignment of a
property value and verifying that a property assignment is actually in a
decorator applied to a class.
This is done so that it will be easier to provide Angular definitions
for decorator properties moving forward. Most immediately, this will
provide decorator class verification for #32238.
PR Close#32252
c624b14e8e