Introduce InsetsSizeOverride

This is to let the insets provider provide a different size to the given
windowing typed window. This can completely replace the ime frame
provider and the old ime frame provider is migrated.

Test: The task bar can still provide correct IME insets
Test: DisplayPolicyInsetsTests
Test: WmTests
Bug: 225200928
Change-Id: I5f8c4462cdc48011efda908e0337a86cbf2a417f