FilesApp crostini: show dialog when sharing root folders

When a user right-clicks and shares a root folder of a volume,
a dialog is shown for the user to confirm the action.

For Drive, the dialog with specific wording for Drive is shown
for My Drive, Team Drives, and Computers.

For other volumes, generic wording is used.

Bug: 878324
Change-Id: I92dad87c8e7b042dd45902d93e08e3cd66abc753
Reviewed-on: https://chromium-review.googlesource.com/c/1337109
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608269}
7 files changed