Add the tests related with obscured flags

Currently, only touch events have implemented the
FLAG_WINDOW_IS_OBSCURED and FLAG_WINDOW_IS_PARTIALLY_OBSCURED flags.
For hover events, we have not implemented these flags. Since hover
events are also motion events, we need to implement these two flags for
the dispatching of hover events as well.

Here, we will first add a test to simulate this situation.

The next issues we need to address are:
- For completely obscured situations, we need to add the
FLAG_WINDOW_IS_OBSCURED flag for hover events.
- For partially obscured situations, we need to add the
FLAG_WINDOW_IS_PARTIALLY_OBSCURED flag for hover events.
- If the window has already received a HOVER_ENTER event, and the mouse
pointer's hover event moves to a position where no window exists, we
need to supplement the window with a HOVER_EXIT event.

Bug: 328160937
Test: atest inputflinger_tests
Flag: TEST_ONLY

Signed-off-by: Linnan Li <lilinnan@xiaomi.corp-partner.google.com>
(cherry picked from https://partner-android-review.googlesource.com/q/commit:4142c41bedbfd1246ee76ce9ff7036e244276831)
Merged-In: I2f0999d4b4e5a55abe81886553843bfa79170167
Change-Id: I2f0999d4b4e5a55abe81886553843bfa79170167