Handle case when snapshot dimensions don't match

If the snapshot starting window has different dimensions than the
snapshots we have taken, we do the following:

- Create a child Surface that has exactly the dimensions of the
snapshot.
- We fill the parent surface with the app background color, as well
as all screen background decorations (status bar background,
navigation bar background).
- We also clip of the status bar/navigation bar background in some
cases, as it looks ugly if it's not behind the system bars.
- Furthermore, we inherit all layout flags on the window and all
layout relevant SystemUI flags on the window such that it's very
likely that the size will match, and the system bars are drawn
correctly.
- In order to make the transition from the snapshot to the real
window a bit more predictable/less messy, we enforce a minimum
duration the snapshot is visible, which is slightly more than our
app transitions.

Test: TaskSnapshotSurfaceTest
Test: Open app, go home, go landscape, open app again
Test: Go to multi-window, open app from recents with a snapshot
taken in fullscreen.

Fixes: 36703868
Change-Id: Ia2d4add6971a18ab7aa2942d2b644d6e87a402af

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