Remove obsolete robolectric test runner integration

The `m Run*RoboTests` test runner is no longer supported, remove the
code to generate the Make rules for it.

Also reduce the number of combining steps by passing the extra jars
that need to be combined into the compile step.

Test: atest --host SystemUiRoboTests
Flag: EXEMPT refactor
Change-Id: Icf05079bf570bed7a10962cbf03459bd53c51f99