Fix IME is beyond the screen if the app doesn't fill its parent bounds

An activity with fixed aspect ratio may not cover the entire screen.
Once the left of the app surface is not the same as the left display
dock frame, the IME will be beyond the screen.

Bug: 128581369
Test: atest DisplayContentTests#testComputeImeParent_app_notMatchParentBounds
Test: manual - Launch a landscape activity with fixed aspect ratio 1.2.
      Click the input field in the activity and check the IME position.

Change-Id: If4125a18042e45efae1f8115008b0374b2669084