Skip version checks when running `flutter upgrade` (#18031)

We were already skipping the check in `flutter upgrade` but this also spawns `flutter precache` and `flutter doctor` which would still check and potentially output the message.

packages/flutter_tools/lib/src/commands/upgrade.dart

@@ -60,7 +60,7 @@ class UpgradeCommand extends FlutterCommand {
     printStatus('Upgrading engine...');
     code = await runCommandAndStreamOutput(
       <String>[
-        fs.path.join('bin', 'flutter'), '--no-color', 'precache',
+        fs.path.join('bin', 'flutter'), '--no-color', '--no-version-check', 'precache',
       ],
       workingDirectory: Cache.flutterRoot,
       allowReentrantFlutter: true
@@ -80,7 +80,7 @@ class UpgradeCommand extends FlutterCommand {
     printStatus('Running flutter doctor...');
     code = await runCommandAndStreamOutput(
       <String>[
-        fs.path.join('bin', 'flutter'), 'doctor',
+        fs.path.join('bin', 'flutter'), '--no-version-check', 'doctor',
       ],
       workingDirectory: Cache.flutterRoot,
       allowReentrantFlutter: true,

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -71,6 +71,11 @@ class FlutterCommandRunner extends CommandRunner<Null> {
         negatable: true,
         hide: !verboseHelp,
         help: 'Whether to use terminal colors.');
+    argParser.addFlag('version-check',
+        negatable: true,
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Allow Flutter to check for updates when this command runs.');
     argParser.addFlag('suppress-analytics',
         negatable: false,
         hide: !verboseHelp,
@@ -280,7 +285,7 @@ class FlutterCommandRunner extends CommandRunner<Null> {
 
         _checkFlutterCopy();
         await FlutterVersion.instance.ensureVersionFile();
-        if (topLevelResults.command?.name != 'upgrade') {
+        if (topLevelResults.command?.name != 'upgrade' && topLevelResults['version-check']) {
           await FlutterVersion.instance.checkFlutterVersionFreshness();
         }