Consider position in isTaskMaximized

This CL makes isTaskMaximized() to check the position as well.
Otherwise, when the window is not at the origin but the size is
maximized, isTaskMaximized() unexpectedly returns true.

Bug: 382021656
Bug: 382990242
Flag: EXEMPT bug fix
Test: DesktopModeWindowDecorViewModelTests
Change-Id: Ie9d8f488fdbcf02c645f6afca132c3c6dbcf762b