Use external/robolectric-shadows/run_robotests.mk

This allows SettingsLib to test against the latest framework changes.

Also replaced TestConfig with traditional robolectric.properties.

Also reworked the test runner to avoid using deprecated API.

Bug: 73173204
Test: make -j56 RunSettingsLibRoboTests
Change-Id: Iebe130d6542ed7096147e3fff61f9cfd76aad948