Change to use support info for interval millis

Add unit tests and fix bugs on no result handling

Bug: 346604998
Flag: android.os.cpu_gpu_headrooms
Test: atest NativeSystemHealthUnitTest SystemHealthManagerUnitTest
            NativeSystemHealthTest HeadroomTest
Change-Id: I7a820c7ccfcbe4c3db2ae0ec81a66c7a55c9add3