feat(folder): Speed up folder size calculations

src/app/rmmapi/messagelist.service.ts

@@ -121,8 +121,11 @@ export class MessageListService {
                 const folderCounts = {};
                 for (const folder of folders) {
                     const path = folder.folderPath;
+
                     if (xapianFolders.has(path)) {
-                        folderCounts[path] = this.searchservice.getMessageCountsForFolder(path);
+                        const res = this.searchservice.api.getFolderMessageCounts(folder.folderName);
+
+                        folderCounts[path] = new FolderMessageCountEntry(res[1], res[0]);
                     } else {
                         folderCounts[path] = FolderMessageCountEntry.of(folder);
                     }

src/app/xapian/rmmxapianapi.ts

@@ -125,6 +125,25 @@ export class XapianAPI {
 
   }
 
+  public getFolderMessageCounts(folder: string): number[] {
+      const $folderString = emAllocateString(folder);
+      const $results = Module._malloc(4 * 2);
+      Module.HEAP8.set(new Uint8Array(4 * 2), $results);
+
+      const ret = Module._getFolderMessageCounts($folderString, $results);
+      let results: number[];
+
+      if (ret !== 0) {
+          results = new Array(2);
+          results[0] = Module.getValue($results, 'i32');
+          results[1] = Module.getValue($results + 4, 'i32');
+      }
+
+      Module._free($folderString);
+      Module._free($results);
+      return results;
+  }
+
   public sortedXapianQuery(querystring: string,
     sortcol: number,
     reverse: number,