Add WindowManagerWrapper class to window decor classes.

The ADDITIONAL_WINDOWS_ABOVE_STATUS_BAR flag currently breaks several
tests due to the app handle using the flag and requiring MONITOR_INPUT
permission due to being a spy window.

This CL changes the method of retrieval of the system WindowManager
service by using a wrapper of the system WindowManager rather than
fetching it directly when needed. This allows us to provide a mock for
tests so we can avoid running into the above permission issue.

Bug: 361411076
Test: atest DesktopModeWindowDecorationTests, HandleMenuTest,
AdditionalSystemViewContainerTest, manual
Flag: EXEMPT bugfix

Change-Id: I3a45a46fe980f409cb8392a2a508ca3c7fb26c89