dartdoc does not obey analysis_options files

[jcollins-g]

#1586 initially assumed that porting over to the analysis driver would make dartdoc obey analysis_options files. This turned out not to be the case, but a new bug was not filed to make it clear that dartdoc does not do that.

[jcollins-g]

This is blocked on the new analyzer API.

[srawlins]

I don't see anything in analysis_options.yaml that should be particularly followed by dartdoc. We can re-open with an example.