Add the ability to edit remote directories over SSH (#14530)

This is a first step towards allowing you to edit remote projects
directly over SSH. We'll start with a pretty bare-bones feature set, and
incrementally add further features.

### Todo

Distribution
* [x] Build nightly releases of `zed-remote-server` binaries
    * [x] linux (arm + x86)
    * [x] mac (arm + x86)
* [x] Build stable + preview releases of `zed-remote-server`
* [x] download and cache remote server binaries as needed when opening
ssh project
* [x] ensure server has the latest version of the binary


Auth
* [x] allow specifying password at the command line
* [x] auth via ssh keys
* [x] UI password prompt

Features
* [x] upload remote server binary to server automatically
* [x] opening directories
* [x] tracking file system updates
* [x] opening, editing, saving buffers
* [ ] file operations (rename, delete, create)
* [ ] git diffs
* [ ] project search

Release Notes:

- N/A

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>

crates/fs/src/fs.rs

@@ -95,8 +95,11 @@ pub trait Fs: Send + Sync {
     fn open_repo(&self, abs_dot_git: &Path) -> Option<Arc<dyn GitRepository>>;
     fn is_fake(&self) -> bool;
     async fn is_case_sensitive(&self) -> Result<bool>;
+
     #[cfg(any(test, feature = "test-support"))]
-    fn as_fake(&self) -> &FakeFs;
+    fn as_fake(&self) -> &FakeFs {
+        panic!("called as_fake on a real fs");
+    }
 }
 
 #[derive(Copy, Clone, Default)]
@@ -602,11 +605,6 @@ impl Fs for RealFs {
         temp_dir.close()?;
         case_sensitive
     }
-
-    #[cfg(any(test, feature = "test-support"))]
-    fn as_fake(&self) -> &FakeFs {
-        panic!("called `RealFs::as_fake`")
-    }
 }
 
 #[cfg(not(target_os = "linux"))]