[reland] aura: test for change to NativeWindowOcclusionTrackerWin

Adds tests for recent change to ensure dragging window is not
considered in occlusion calculations.
Specifically
https://chromium-review.googlesource.com/c/chromium/src/+/3149714 .

This test generates a mouse down event on the titlebar followed by
a move. This is done to move the window in the same way the user moves
the window. On windows 7 the mouse down was being clicked on the icon,
triggering a context menu to be shown. The fix is to change the location
of the mouse event so that it doesn't hit the window icon.

Change-Id: Ic7eab8cee7d3111dafcb8929411ca4833642aed9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3193876
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: David Bienvenu <davidbienvenu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#927754}

• ui/aura/BUILD.gn[diff]
• ui/aura/native_window_occlusion_tracker_win_interactive_test.cc[diff]