Notify the user that we're collecting symbols

It could be confusing if they see "Indexing n/n" but cache priming does not finish.

Author: ChayimFriedman2

src/tools/rust-analyzer/crates/ide-db/src/prime_caches.rs

@@ -202,7 +202,7 @@ pub fn parallel_prime_caches(
                     crates_currently_indexing: vec![],
                     crates_done: crate_def_maps_done,
                     crates_total: crate_def_maps_done,
-                    work_type: "Indexing",
+                    work_type: "Done",
                 });
                 return;
             }
@@ -226,6 +226,15 @@ pub fn parallel_prime_caches(
                     }
                 }
 
+                if crate_def_maps_done == crate_def_maps_total {
+                    cb(ParallelPrimeCachesProgress {
+                        crates_currently_indexing: vec![],
+                        crates_done: crate_def_maps_done,
+                        crates_total: crate_def_maps_done,
+                        work_type: "Collecting Symbols",
+                    });
+                }
+
                 let origin = &crate_id.data(db).origin;
                 if origin.is_lang() {
                     crate_import_maps_total += 1;