Modify getUserAssignedToDisplay to handle the extra displays

Extra displays such as the overlay display and the virtual display
can be assigned to a user when they are created at runtime in the
automotive multi-user multi-display environment.
However, getUserAssignedToDisplay does not account for the extra
displays, causing it to return the current user instead of the user assigned to them.
To address this issue, it is modified to return the user assigned
to the extra displays.

Flag: EXEMPT (bug fix)
Bug: 362325749
Test: atest CtsWindowManagerDeviceActivity:ActivityLifecycleTopResumedStateTests#testFinishOnDifferentDisplay_nonFocused
Test: atest --user-type secondary_user CtsWindowManagerDeviceActivity:ActivityLifecycleTopResumedStateTests#testFinishOnDifferentDisplay_nonFocused
Test: atest --user-type secondary_user_on_secondary_display CtsWindowManagerDeviceActivity:ActivityLifecycleTopResumedStateTests#testFinishOnDifferentDisplay_nonFocused
Test: atest FrameworksMockingServicesTests:com.android.server.pm.UserVisibilityMediatorMUMDTest FrameworksMockingServicesTests:com.android.server.pm.UserVisibilityMediatorMUPANDTest FrameworksMockingServicesTests:com.android.server.pm.UserVisibilityMediatorSUSDTest

Signed-off-by: Dohyun Lee <dohyun.lee@lge.com>
(cherry picked from https://partner-android-review.googlesource.com/q/commit:259e0544ec718daa9a4f62362433c5b0fe63bcbb)
Merged-In: I1a9d5f3aace8b72b95e216f3780ede5533473ffc
Change-Id: I1a9d5f3aace8b72b95e216f3780ede5533473ffc