Treat all docs issues (except hidden superclass) as errors

Ideally we'd enable a couple of the default hidden ones that are nice
to have, but doclava insists on emitting errors for the entire framework
rather than just the support library sources. Such is doclava.

Bug: 33202068
Test: ./gradlew generateDocs
Change-Id: I9eb3775527667915abed9eb4ea9cb44dbb3626e6
2 files changed