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/ui/src/components/icon.rs

@@ -93,6 +93,7 @@ pub enum IconName {
     Option,
     PageDown,
     PageUp,
+    Play,
     Plus,
     Public,
     Quote,
@@ -185,6 +186,7 @@ impl IconName {
             IconName::Option => "icons/option.svg",
             IconName::PageDown => "icons/page_down.svg",
             IconName::PageUp => "icons/page_up.svg",
+            IconName::Play => "icons/play.svg",
             IconName::Plus => "icons/plus.svg",
             IconName::Public => "icons/public.svg",
             IconName::Quote => "icons/quote.svg",