Allow canceling in-progress language server work (e.g. cargo check) (#13173)

Release Notes:

- Added a more detailed message in place of the generic `checking...`
messages when Rust-analyzer is running.
- Added a rate limit for language server status messages, to reduce
noisiness of those updates.
- Added a `cancel language server work` action which will cancel
long-running language server tasks.

---------

Co-authored-by: Richard <richard@zed.dev>

crates/gpui/src/executor.rs

@@ -13,7 +13,7 @@ use std::{
         Arc,
     },
     task::{Context, Poll},
-    time::Duration,
+    time::{Duration, Instant},
 };
 use util::TryFutureExt;
 use waker_fn::waker_fn;
@@ -316,6 +316,14 @@ impl BackgroundExecutor {
         }
     }
 
+    /// Get the current time.
+    ///
+    /// Calling this instead of `std::time::Instant::now` allows the use
+    /// of fake timers in tests.
+    pub fn now(&self) -> Instant {
+        self.dispatcher.now()
+    }
+
     /// Returns a task that will complete after the given duration.
     /// Depending on other concurrent tasks the elapsed duration may be longer
     /// than requested.