Stop using internal analyzer/lib/src/utilities/extensions/element.dart #4052
Description
It looks that https://dart-review.googlesource.com/c/sdk/+/430261 breaks because DartDoc uses analyzer/lib/src/utilities/extensions/element.dart to access metadata (which used to be the list of annotations). However the CL renames metadata2 to metadata, so the extension is not applicable anymore. Anyway, internal libraries should not be imports.