Use external/robolectric-shadows/run_robotests.mk

This allows Settings to test against the latest framework changes.

Also replaced TestConfig with traditional robolectric.properties.

Bug: 73173204
Bug: 73892008
Test: make -j56 RunSettingsRoboTests
Change-Id: I3135b4fa5f095ba79b282a76f45dd9baa2584bc7