Add new unit tests for battery_saver_supported_check_api flag

Bug: 305067031
Test: atest PowerManagerTest
arm64-v8a FrameworksCoreTests: Passed: 14, Failed: 0, Ignored: 0, Assumption Failed: 0

Change-Id: Ib28f104acbf06c9cf0ed04a8e48551195b83a423
1 file changed