[lldb-dap] Fix typescript issue in updated typescript code. (llvm#156117)

After PR 155021 landed, some typescript 'promises' in async functions
were not 'await'ed, which caused us some build failures. This fixes that
by adding 'await' in the appropriate places.

(cherry picked from commit 6d43551)

Author: cmtice

lldb/tools/lldb-dap/src-ts/ui/symbols-provider.ts

@@ -61,18 +61,18 @@ export class SymbolsProvider extends DisposableContext {
       return;
     }
 
-    this.showSymbolsForModule(session, selectedModule.module);
+    await this.showSymbolsForModule(session, selectedModule.module);
   }
 
   private async showSymbolsForModule(session: vscode.DebugSession, module: DebugProtocol.Module) {
     try {
       const symbols = await this.getSymbolsForModule(session, module.id.toString());
-      this.showSymbolsInNewTab(module.name.toString(), symbols);
+      await this.showSymbolsInNewTab(module.name.toString(), symbols);
     } catch (error) {
       if (error instanceof Error) {
-        vscode.window.showErrorMessage("Failed to retrieve symbols: " + error.message);
+        await vscode.window.showErrorMessage("Failed to retrieve symbols: " + error.message);
       } else {
-        vscode.window.showErrorMessage("Failed to retrieve symbols due to an unknown error.");
+        await vscode.window.showErrorMessage("Failed to retrieve symbols due to an unknown error.");
       }
 
       return;
@@ -106,7 +106,7 @@ export class SymbolsProvider extends DisposableContext {
     const symbolsTableScriptPath = panel.webview.asWebviewUri(vscode.Uri.joinPath(this.getExtensionResourcePath(), "symbols-table-view.js"));
 
     panel.webview.html = getSymbolsTableHTMLContent(tabulatorJsPath, tabulatorCssPath, symbolsTableScriptPath);
-    panel.webview.postMessage({ command: "updateSymbols", symbols: symbols });
+    await panel.webview.postMessage({ command: "updateSymbols", symbols: symbols });
   }
 
   private getExtensionResourcePath(): vscode.Uri {