Reuse StateChange logic in SysUIState

StateChange logic was extracted to implement SysUIStateOverride. It can be used also in the plain SysUIState, reducing duplication and increasing readability.

+ Ensure only a single bit is on when setting a flag. All prod code seems to do it already. Updating a couple of tests to match this reality as well.

Bug: 362719719
Bug: 398011576
Test: SysUiStateImplTest, SysUIStateDispatcherTest
Flag: com.android.systemui.shade_window_goes_around
Change-Id: I8fac16d94f9a8ac6705d092d2dd055206eac88f0