fc-queue-runner: plumb worker_count into fair-share scheduling

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I1f7f295bd7c2cbf46b64b22a3417ccc06a6a6964

crates/queue-runner/src/worker.rs

@@ -102,6 +102,10 @@ impl WorkerPool {
     .await;
   }
 
+  pub fn worker_count(&self) -> usize {
+    self.worker_count
+  }
+
   pub fn active_builds(&self) -> &ActiveBuilds {
     &self.active_builds
   }