Update SliceContollerInXmlTest to match latest slice spec.

- Convert the test to use CodeInspector
- Skip abstract classes when validating contract
- Also check SliderPreferenceController when validating contract

Change-Id: I671c1a622df6d1d7248a12932f144711fbf5a026
Fixes: 77634230
Test: make RunSettingsRoboTests -j40 ROBOTEST_FILTER=CodeIns
3 files changed