Avoid building RollbackTestApps into the device image.

The current approach for including built apks as java resources in
RollbackTest.apk appears to cause the RollbackTestApp apks to be
included in the device release image. Convert the Android.mk for
RollbackTest to Android.bp to work around this issue.

This breaks the split apk tests, but we can figure out how to address
that later. Marking the split apk tests @Ignore for now.

Bug: 123695037
Bug: 127520966
Test: make -j80 dist tests, verify no RollbackT*.apk is included in the
      built device image.
Test: atest RollbackTest; atest StagedRollbackTest, verify no
      RollbackT*.apk is included in the built system image.

Change-Id: Ib413785b0974faddf19ac8dd7387b2642dab37e4