Add static Runnables (#8009)

Part of #7108

This PR includes just the static runnables part. We went with **not**
having a dedicated panel for runnables.
This is just a 1st PR out of N, as we want to start exploring the
dynamic runnables front. Still, all that work is going to happen once
this gets merged.

Release Notes:

- Added initial, static Runnables support to Zed. Such runnables are defined in
`runnables.json` file (accessible via `zed: open runnables` action) and
they can be spawned with `runnables: spawn` action.

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Pitor <pitor@zed.dev>
Co-authored-by: Beniamin <beniamin@zagan.be>

crates/workspace/src/workspace.rs

@@ -50,6 +50,7 @@ pub use persistence::{
 };
 use postage::stream::Stream;
 use project::{Project, ProjectEntryId, ProjectPath, Worktree, WorktreeId};
+use runnable::SpawnInTerminal;
 use serde::Deserialize;
 use settings::Settings;
 use shared_screen::SharedScreen;
@@ -108,7 +109,6 @@ actions!(
         FollowNextCollaborator,
         NewTerminal,
         NewCenterTerminal,
-        ToggleTerminalFocus,
         NewSearch,
         Feedback,
         Restart,
@@ -464,6 +464,7 @@ pub enum Event {
     PaneAdded(View<Pane>),
     ContactRequestedJoin(u64),
     WorkspaceCreated(WeakView<Workspace>),
+    SpawnRunnable(SpawnInTerminal),
 }
 
 pub enum OpenVisible {