Not measuring latency when fold event results in screen off

- changing toState: now screen off or state AOD means that it just ended up in the state, not necessarily because of folding
- if final state is screen off we don’t care about latency - which fixes the problem of very small latencies coming from case when we’re folding while screen is off
- filling out “fromState” field in DisplaySwitchLatencyEvent
- updating javadoc to clarify that Switching doesn’t necessarily mean we’re turning on/off any display
- small fixes in tests - removing not needed setScreenPowerState and simplifying some tests

Bug: 394257187
Flag: NONE multiple small changes
Test: DisplaySwitchLatencyTrackerTest
Change-Id: Id5b92d23d9f2b41b24a8a69851e4dc0d86f7838e