Final (?!?!?!?!) Directory Access improvements.

- Hide children items when parent is granted access (and vice versa).
- Added dividers in between volumes.

Test: manual verification
Test: atest CtsAppSecurityHostTestCases:ScopedDirectoryAccessTest#testResetDoNotAskAgain,testResetGranted

Bug: 72055774

Change-Id: Ie4ad117d1f8a53bf7dbf7747e768a301b0d03604