This fixes the offline Dash/Zeal docs generation to use the newly added dartdoc markers for different entity types to make it more exact when finding entity names.
Bumped Dartdoc to the next release.
(re-land of #24244)
This generates a zip file containing all of the docs, and uploads it when we publish docs, as well as a
Dash/Zeal docset that contains a feed of the docs.
Addresses at least part of #9955
