fix(source_metadata_extractor): Fixed problem with processing Component and Decorator annotations when named import is used.

This change related to issue #1620. 
Please review if this solution is acceptable.
Thanks.
This could match `FooComponent` and `FooDecorator`.  Pavel's comment already alludes to the fact that the check isn't that safe, but a safer check would be (assuming the library prefix is part of the name):

    final exp = new RegExp(r"\.?(Component|Decorator)$");
    if (!exp.hasMatch(ann.name.name))