Support test skipping when power save modes aren't enabled.

Some classes of devices will not have auto power save modes enabled. On
those devices, we should skip tests that require the modes be enabled.

Bug: 240108412
Bug: 240630396
Test: Manually go through CTS-V "Ignore Battery Optimizations Test"
Test: atest CtsUsageStatsTestCases:UsageStatsTest
Change-Id: Icc64fbe75213386a1f41fae258e50c4032920b0a