Clients have been updated to use ext-workspace-v1 and
cosmic-workspace-v2.
Removing this should save some duplication of having to update both
cosmic workspace v1 and ext workspace code, and should help with things
like using the same workspace handle when a workspace moves to a
different group (which is something that was changed before the final
version of the ext-workspace-v1 protocol.)
This new protocol extends `ext-workspace-v1` with the same additional
functionality `cosmic-workspace-v1` provided. Toplevel info and toplevel
management are also updated to use ext handles, and there's an image
source for ext workspaces.
For now, the old protocol is still supported.
`from_raw_parts()` is only sound if the alignment is the same, so it
can't be used to covert to a `Vec<u8>` from a type with a greater
alignment.
This isn't hard to avoid, luckily.
