Add SystemClock (#8239)

This PR adds a `SystemClock` trait for abstracting away the system
clock.

This allows us to swap out the real system clock with a
`FakeSystemClock` in the tests, thus allowing the fake passage of time.

We're using this in `Telemetry` to better mock the clock for testing
purposes.

Release Notes:

- N/A

crates/zed/Cargo.toml

@@ -34,6 +34,7 @@ channel.workspace = true
 chrono = "0.4"
 cli.workspace = true
 client.workspace = true
+clock.workspace = true
 collab_ui.workspace = true
 collections.workspace = true
 command_palette.workspace = true

crates/zed/src/main.rs

@@ -140,9 +140,10 @@ fn main() {
         handle_keymap_file_changes(user_keymap_file_rx, cx);
         client::init_settings(cx);
 
+        let clock = Arc::new(clock::RealSystemClock);
         let http = http::zed_client(&client::ClientSettings::get_global(cx).server_url);
 
-        let client = client::Client::new(http.clone(), cx);
+        let client = client::Client::new(clock, http.clone(), cx);
         let mut languages = LanguageRegistry::new(login_shell_env_loaded);
         let copilot_language_server_id = languages.next_language_server_id();
         languages.set_executor(cx.background_executor().clone());