Support robolectric_test

robolectric_test will compile a suite of tests that run in
robolectric.  For now it also generates a Run* rule, later
that will be removed in favor of atest.

Bug: 123248659
Test: m RunSettingsLibRoboTests
Change-Id: I12407d0b0d639e31c1969077ba787e8985e6a506