Expose safe region letterboxing information to shell

- Add the info in app compat task info.
- Clean up logic of if safe region letterboxing is applied or not.

Bug: 412695008
Test: atest CtsWindowManagerJetpackTestCases WmTests:SizeCompatTests WmTests:AppCompatUtilsTest WmTests:AppCompatLetterboxPolicyTest WmTests:WindowOrganizerTests WmTests:WindowContainerTests WmTests:AppCompatSafeRegionPolicyTests WmTests:WindowContainerTransactionTests
Test: manual, verify caption bar with safe region when activity
embedding and WM property of not allowing safe region letterboxing
Flag: EXEMPT (bug fix)

Change-Id: I9ea19d0c53c9cfbf5c43f27313a28b67f4562db7