Allow disk-based diagnostic progress begin/end events to interleave

When multiple saves occur, we can have multiple start events followed by multiple end events. We don't want to update our project diagnostics view until all pending progress is finished.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>

crates/lsp/src/lsp.rs

@@ -514,6 +514,22 @@ impl FakeLanguageServer {
         notification.params
     }
 
+    pub async fn start_progress(&mut self, token: impl Into<String>) {
+        self.notify::<notification::Progress>(ProgressParams {
+            token: NumberOrString::String(token.into()),
+            value: ProgressParamsValue::WorkDone(WorkDoneProgress::Begin(Default::default())),
+        })
+        .await;
+    }
+
+    pub async fn end_progress(&mut self, token: impl Into<String>) {
+        self.notify::<notification::Progress>(ProgressParams {
+            token: NumberOrString::String(token.into()),
+            value: ProgressParamsValue::WorkDone(WorkDoneProgress::End(Default::default())),
+        })
+        .await;
+    }
+
     async fn send(&mut self, message: Vec<u8>) {
         self.stdout
             .write_all(CONTENT_LEN_HEADER.as_bytes())