Change opacity of the drag indicator according to the cursor position

This CL makes the drag indicator change the opacity of itself if the
cursor is on a different display.

Bug: 383240504
Test: WMShellUnitTests
Test: go/cd-smoke
Flag: com.android.window.flags.enable_connected_displays_window_drag
Change-Id: I3e31ef55d78619e2851af75dbeb357495fce518d