Add initial CI job for Windows target (#8088)

Clippy is disabled for now, due to many warnings in both `gpui` and
other code, see
https://github.com/zed-industries/zed/actions/runs/7980269779/job/21789529800
for more details.

Also, due to `#!/usr/bin/env bash` shebang in the `script/clippy`, it
starts in Windows CI with `shell: C:\Program Files\Git\bin\bash.EXE
-euxo pipefail {0}`

https://github.com/zed-industries/zed/actions/runs/7980269779/job/21789529800#step:4:3
It seems more appropriate to use PowerShell instead.

See `todo!("windows")` for all stubbed places currently.

Release Notes:

- N/A

crates/gpui/src/platform/test/platform.rs

@@ -125,6 +125,9 @@ impl Platform for TestPlatform {
 
         #[cfg(target_os = "macos")]
         return Arc::new(crate::platform::mac::MacTextSystem::new());
+
+        #[cfg(target_os = "windows")]
+        todo!("windows")
     }
 
     fn run(&self, _on_finish_launching: Box<dyn FnOnce()>) {