Integrate insets compat override with other overrides

Before this change, the major override was done independently in
ActivityRecord. It causes some conflicts between the override and other
compat sandboxing overrides. Make the override happens after the
sandboxing strategy calculation is done, and merge the override logic
into computeConfigResourceOverrides to avoid conflicts. Also it will
reduce the redundant code to recalculate configuration fields from the
bounds again.

Test: DisplayPolicyInsetsTests
Test: AspectRatioSdk25Tests
Bug: 336687188
Change-Id: If9f1df72f4fde92017dbf547b56f7cd8c9766b2f