Allow Overlay Display to take display flags

Before, CTS test used WindowManager#shouldShowSystemDecors() to set show
system decorations after overlay display launched, which wouldn't enable
system decorations without relaunching. Now, we can set those flag
before display launch similar to what VirtualDisplayHelper does.

Bug: 153624902
Bug: 154158053
Test: atest CtsWindowManagerDeviceTestCases:MultiDisplayClientTests
Test: atest CtsWindowManagerDeviceTestCases:MultiDisplaySystemDecorationTests
Change-Id: I83c21a74c722a23ac77141305a08d9f67c5bbcf0