[18/n] Extract applyAspectRatio logic

Extract aspect ratio logic from ActivityRecord moving
it into AppCompatAspectRatioPolicy.

Flag: EXEMPT refactor
Bug: 350513585
Test: atest WmTests:ActivityRecordTests
Test: atest WmTests:DualDisplayAreaGroupPolicyTest
Test: atest WmTests:LetterboxUiControllerTest
Test: atest WmTests:RootWindowContainerTests
Test: atest WmTests:SizeCompatTests
Test: atest WmTests:TaskFragmentTest

Change-Id: I003eb49e351dfa1be4e30f1095b02712c99b1d64