Adds support for cosmic-workspace-v2 pin, unpin, move_after, and
move_before requests.
Both features need some work with workspaces span displays mode, so that
will need more fixes later.
We also want to generate a unique id for pinned workspaces to send in
the ext-workspace-v1 protocol. But that isn't a strict requirement for
anything. So I haven't yet fully implemented that. We'll also want to
persist other things, like workspace naming when that's added.
Overall, though, with separate workspaces per display, this is working
pretty well.
It seems to derive `CosmicConfigEntry`, we need to use `_` in property
names, because `_` isn't mapped to `-` and there doesn't seem to be a
mechanism like `#[serde(rename)]`.
It seems good to be consistent anyway. So this seems good to change,
unless we really like using `-` for names on disk, then cosmic-panel
needs to be changed.
`CosmicConfigEntry` also requires `PartialEq`, which is easy enough to
add.
This will break existing input settings, which will have to be
re-applied with the new locations. Cosmic-settings also need to be
updated for this.
