Remove WindowConfiguration#mDisplayWindowingMode

Integrate the logic into
ActivityRecord#shouldCreateCompatDisplayInsets().
It is OK to do it because WindowConfiguration#hasWindowDecorCaption()
isn't used by anyone to determine the visibility of captions, and to
make this logic an explicity policy in WM core.

Bug: 333724879
Test: Build & presubmit tests
Change-Id: I526620a182e1915628bf381454dd9247a8c3639f