Add close_to_square_config_includes_status_bar flag

This is a feature flag to control the effort of eliminating letterbox
cases for close-to-square displays. Additional config flag and app
compat flag will be introduced to achieve the full policy control.

Test: m services.core.flags-java
Test: m services.core.unboosted
Test: m dist
Bug: 291870756
Change-Id: Ic49a2148bd30b19bd4f56eebf15fa4ffc925947d