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/gpui/src/platform/mac/platform.rs

@@ -24,6 +24,7 @@ use core_foundation::{
     boolean::CFBoolean,
     data::CFData,
     dictionary::{CFDictionary, CFDictionaryRef, CFMutableDictionary},
+    runloop::CFRunLoopRun,
     string::{CFString, CFStringRef},
 };
 use ctor::ctor;
@@ -139,6 +140,7 @@ pub(crate) struct MacPlatformState {
     foreground_executor: ForegroundExecutor,
     text_system: Arc<MacTextSystem>,
     renderer_context: renderer::Context,
+    headless: bool,
     pasteboard: id,
     text_hash_pasteboard_type: id,
     metadata_pasteboard_type: id,
@@ -155,15 +157,16 @@ pub(crate) struct MacPlatformState {
 
 impl Default for MacPlatform {
     fn default() -> Self {
-        Self::new()
+        Self::new(false)
     }
 }
 
 impl MacPlatform {
-    pub(crate) fn new() -> Self {
+    pub(crate) fn new(headless: bool) -> Self {
         let dispatcher = Arc::new(MacDispatcher::new());
         Self(Mutex::new(MacPlatformState {
             background_executor: BackgroundExecutor::new(dispatcher.clone()),
+            headless,
             foreground_executor: ForegroundExecutor::new(dispatcher),
             text_system: Arc::new(MacTextSystem::new()),
             renderer_context: renderer::Context::default(),
@@ -394,7 +397,15 @@ impl Platform for MacPlatform {
     }
 
     fn run(&self, on_finish_launching: Box<dyn FnOnce()>) {
-        self.0.lock().finish_launching = Some(on_finish_launching);
+        let mut state = self.0.lock();
+        if state.headless {
+            drop(state);
+            on_finish_launching();
+            unsafe { CFRunLoopRun() };
+        } else {
+            state.finish_launching = Some(on_finish_launching);
+            drop(state);
+        }
 
         unsafe {
             let app: id = msg_send![APP_CLASS, sharedApplication];
@@ -1238,7 +1249,7 @@ mod tests {
     }
 
     fn build_platform() -> MacPlatform {
-        let platform = MacPlatform::new();
+        let platform = MacPlatform::new(false);
         platform.0.lock().pasteboard = unsafe { NSPasteboard::pasteboardWithUniqueName(nil) };
         platform
     }