Migrate frameworks/base javadocs references to androidx

Does not remove Support Library artifacts from docs classpath (ApiDocs.bp)
because they are still used in development/samples, which is not as easy
to migrate as javadoc.

Bug: 158779503
Test: make docs
Exempt-From-Owner-Approval: Mass find/replace for androidx migration
Change-Id: Icf7f53ec36a0e970413352e2ebf40ce9d60ed17e