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/language/src/buffer.rs

@@ -372,7 +372,7 @@ pub trait File: Send + Sync {
     fn as_any(&self) -> &dyn Any;
 
     /// Converts this file into a protobuf message.
-    fn to_proto(&self) -> rpc::proto::File;
+    fn to_proto(&self, cx: &AppContext) -> rpc::proto::File;
 
     /// Return whether Zed considers this to be a private file.
     fn is_private(&self) -> bool;
@@ -612,10 +612,10 @@ impl Buffer {
     }
 
     /// Serialize the buffer's state to a protobuf message.
-    pub fn to_proto(&self) -> proto::BufferState {
+    pub fn to_proto(&self, cx: &AppContext) -> proto::BufferState {
         proto::BufferState {
             id: self.remote_id().into(),
-            file: self.file.as_ref().map(|f| f.to_proto()),
+            file: self.file.as_ref().map(|f| f.to_proto(cx)),
             base_text: self.base_text().to_string(),
             diff_base: self.diff_base.as_ref().map(|h| h.to_string()),
             line_ending: proto::serialize_line_ending(self.line_ending()) as i32,
@@ -3940,7 +3940,7 @@ impl File for TestFile {
         unimplemented!()
     }
 
-    fn to_proto(&self) -> rpc::proto::File {
+    fn to_proto(&self, _: &AppContext) -> rpc::proto::File {
         unimplemented!()
     }