wayland: Handle dragging from/dropping to v1 data device users

Interoperation between wl_data_device_manager v1 and v3 got broken
at some point. Ensure that we resort to the "copy" action if either
the drop site or the drag source are from a client that requested v1.

Closes: #965

(cherry picked from commit ffad55c6)
4 jobs for gnome-3-34 in 6 minutes and 53 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #575265
build-mutter

00:04:04

passed #575266
build-without-native-backend-and-wayland

00:02:30

 
  Test
passed #575268
can-build-gnome-shell

00:01:17

passed #575267
test-mutter

00:02:49