Add basic proxy settings (#11852)

Adding `proxy` keyword to configure proxy while using zed. After setting
the proxy, restart Zed to acctually use the proxy.

Example setting: 
```rust
"proxy" = "socks5://localhost:10808"
"proxy" = "http://127.0.0.1:10809"
```

Closes #9424, closes #9422, closes #8650, closes #5032, closes #6701,
closes #11890

Release Notes:

- Added settings to configure proxy in Zed

---------

Co-authored-by: Jason Lee <huacnlee@gmail.com>

crates/zed/src/main.rs

@@ -343,6 +343,7 @@ fn main() {
 
         client::init_settings(cx);
         let client = Client::production(cx);
+        cx.update_http_client(client.http_client().clone());
         let mut languages =
             LanguageRegistry::new(login_shell_env_loaded, cx.background_executor().clone());
         languages.set_language_server_download_dir(paths::LANGUAGES_DIR.clone());