Update sharesheet for large devices

Switches to a wrapped sharesheet (instead of filling the screen)
and 6 columns instead of 8 for large screens. Also fixes some
small details with the appearance (see
https://docs.google.com/presentation/d/1WDbmWx6uXaFi8jos7Sp6ZUmBh24Y5Bj5G7dW78LxE40/edit#slide=id.gb836e06a0c_0_0)

Bug: 195102471
Test: manual (visual changes)
Merged-In: I5d84dce0aea7657a50dc3376be9d8b5e41b907db
Change-Id: I5d84dce0aea7657a50dc3376be9d8b5e41b907db