Ask for confirmation before importing from vcard

But only when vcard import is started from outside
the contacts application itself.

Test: Manually confirmed the following behavior

1. When there is 0 or 1 writable contacts providing
   account on the device:
  - Importing contacts from the contacts app itself
    DOES NOT SHOW the new confirmation dialog.  On M+
    devices, if the storage permission has not been
    previously granted or dismissed, the new confirmation
    dialog is also NOT SHOWN after granting the storage
    permission.
  - Sending a vcard to contacts from another application
    DOES SHOW the new confirmation dialog.  On M+
    devices, if the storage permission has not been
    previously granted or dismissed, the new confirmation
    dialog is also SHOWN after granting the storage
    permission.

2. When there are 2 or more writable contacts providing
   accounts on the device:
  - Importing contacts from the contacts app itself
    DOES NOT SHOW the new confirmation dialog, instead the
    existing account picker dialog is displayed.  On M+
    devices, if the storage permission has not been
    previously granted or dismissed, the new confirmation
    dialog is also NOT SHOWN after granting the storage
    permission.
  - Sending a vcard to contacts from another application
    DOES NOT SHOW the new confirmation dialog, instead the
    existing account picker dialog is displayed.  On M+
    devices, if the storage permission has not been
    previously granted or dismissed, sending a vcard to
    contacts from another application also DOES NOT SHOW
    the new confirmation dialog.

Bug: 32219099

Change-Id: I0310c6e35cb378e1fe22691e5aecdb8ece1a3c9e