fix(core): nx add should show errors (nrwl#28079)

`nx add` errors should be surfaced to users.

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## Current Behavior
Users do not see errors from init generator.

## Expected Behavior
Users see errors from init generator.

## Related Issue(s)
<!-- Please link the issue being fixed so it gets closed when this is
merged. -->

Fixes #

Author: jaysoo

packages/nx/src/command-line/add/add.ts

@@ -141,7 +141,7 @@ async function initializePlugin(
   } catch (e) {
     spinner.fail();
     output.addNewline();
-    logger.error(e.message);
+    logger.error(e);
     output.error({
       title: `Failed to initialize ${pkgName}. Please check the error above for more details.`,
     });

packages/nx/src/utils/child-process.ts

@@ -37,7 +37,7 @@ export function runNxSync(
 export async function runNxAsync(
   cmd: string,
   options?: ExecOptions & { cwd?: string; silent?: boolean }
-) {
+): Promise<void> {
   let baseCmd: string;
   if (existsSync(join(workspaceRoot, 'package.json'))) {
     baseCmd = `${getPackageManagerCommand().exec} nx`;
@@ -59,15 +59,15 @@ export async function runNxAsync(
   if (options?.silent) {
     delete options.silent;
   }
-  await new Promise((resolve, reject) => {
+  return new Promise<void>((resolve, reject) => {
     const child = exec(
       `${baseCmd} ${cmd}`,
       options,
       (error, stdout, stderr) => {
         if (error) {
-          reject(error);
+          reject(stderr || stdout || error.message);
         } else {
-          resolve(stdout);
+          resolve();
         }
       }
     );