Fix AccessibilityWindowManager#dump outputs duplicated entry in multi-display

Currently, focus related state is dumped for each display, but they're
managed globally in Ac11yWindowManager, not per display in
DisplayWindowsObserver.

dump of these variables should be done only once in A11yWindowManager.

Bug: none
Test: dumpsys accessibility
Change-Id: Ib8f6fe02ee9ee83eb6de3f459388c8ff7e58f71e