Add action chips to corner screenshot flow

In the corner screenshot flow, add a LinearLayout with action chips
(share/edit/scroll) that pops up once the actions are available.

Note that the 'scroll' button currently does nothing.

Bug: 144918886
Test: manual; tested that 'edit' and 'share' chips open the
appropriate apps and make the screenshot disappear; tested that
current notification flow is unchanged.

Change-Id: I6952b76aa3bb479c49b1905275d5fcdc0eeaf2df