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/terminal/Cargo.toml

@@ -24,6 +24,7 @@ libc = "0.2"
 mio-extras = "2.0.6"
 ordered-float.workspace = true
 procinfo = { git = "https://github.com/zed-industries/wezterm", rev = "5cd757e5f2eb039ed0c6bb6512223e69d5efc64d", default-features = false }
+runnable.workspace = true
 schemars.workspace = true
 serde.workspace = true
 serde_derive.workspace = true