Bazel: Consume mockito library from plugin API

Since release 3.0.1, the mockito library (and its dependencies) is part
of the plugin API and thus should not be included anymore as custom

Update bazlets to latest stable-3.0. However switch the plugin api from
release to snapshot until the above API change gets formally released.

Change-Id: I97918778c8786c2a9d807ec9b47dca639a643b22
3 files changed