fix(ignoreSnapshots): print a notice when ignoreSnapshots option is on (

microsoft#17317)

<img width="1161" alt="image"
src="https://user-images.githubusercontent.com/746130/190032155-ae454c3e-1a7d-4a64-8cd6-bb27f9075ef3.png">

packages/playwright-test/src/runner.ts

@@ -29,6 +29,7 @@ import { Loader } from './loader';
 import type { FullResult, Reporter, TestError } from '../types/testReporter';
 import { Multiplexer } from './reporters/multiplexer';
 import { formatError } from './reporters/base';
+import { colors } from 'playwright-core/lib/utilsBundle';
 import DotReporter from './reporters/dot';
 import GitHubReporter from './reporters/github';
 import LineReporter from './reporters/line';
@@ -401,6 +402,15 @@ export class Runner {
     if (result.status !== 'passed')
       return result;
 
+    if (config._ignoreSnapshots) {
+      this._reporter.onStdOut?.(colors.dim([
+        'NOTE: running with "ignoreSnapshots" option. All of the following asserts are silently ignored:',
+        '- expect().toMatchSnapshot()',
+        '- expect().toHaveScreenshot()',
+        '',
+      ].join('\n')));
+    }
+
     // 14. Run tests.
     try {
       const sigintWatcher = new SigIntWatcher();