Replace references to droiddoc with droidstubs

The java_sdk_library code used to create droiddoc and now it creates
droidstubs but it still referenced droiddoc internally. This change
removed all the remaining references except the ones that are visible
externally.

Bug: 153443117
Bug: 153306490
Test: m nothing
Merged-In: Ie883eb4590f9c091d4149d7b17d7d3d91b1b5c6a
Change-Id: Ie883eb4590f9c091d4149d7b17d7d3d91b1b5c6a