[flutter_plugin_tools] Remove --skip flag

The xctest command has a --skip flag that is redundant with the general
--exclude flag.

Part of flutter/flutter#83413

Author: stuartmorgan-g

script/tool/lib/src/xctest_command.dart

@@ -14,7 +14,6 @@ import 'package:path/path.dart' as p;
 import 'common.dart';
 
 const String _kiOSDestination = 'ios-destination';
-const String _kSkip = 'skip';
 const String _kXcodeBuildCommand = 'xcodebuild';
 const String _kXCRunCommand = 'xcrun';
 const String _kFoundNoSimulatorsMessage =
@@ -36,8 +35,6 @@ class XCTestCommand extends PluginCommand {
           'this is passed to the `-destination` argument in xcodebuild command.\n'
           'See https://developer.apple.com/library/archive/technotes/tn2339/_index.html#//apple_ref/doc/uid/DTS40014588-CH1-UNIT for details on how to specify the destination.',
     );
-    argParser.addMultiOption(_kSkip,
-        help: 'Plugins to skip while running this command. \n');
   }
 
   @override
@@ -59,8 +56,6 @@ class XCTestCommand extends PluginCommand {
       destination = 'id=$simulatorId';
     }
 
-    final List<String> skipped = getStringListArg(_kSkip);
-
     final List<String> failingPackages = <String>[];
     await for (final Directory plugin in getPlugins()) {
       // Start running for package.
@@ -72,11 +67,6 @@ class XCTestCommand extends PluginCommand {
         print('\n\n');
         continue;
       }
-      if (skipped.contains(packageName)) {
-        print('$packageName was skipped with the --skip flag.');
-        print('\n\n');
-        continue;
-      }
       for (final Directory example in getExamplesForPlugin(plugin)) {
         // Running tests and static analyzer.
         print('Running tests and analyzer for $packageName ...');

script/tool/test/xctest_command_test.dart

@@ -83,7 +83,6 @@ final Map<String, dynamic> _kDeviceListMap = <String, dynamic>{
 
 void main() {
   const String _kDestination = '--ios-destination';
-  const String _kSkip = '--skip';
 
   group('test xctest_command', () {
     FileSystem fileSystem;
@@ -121,7 +120,7 @@ void main() {
       expect(processRunner.recordedCalls, orderedEquals(<ProcessCall>[]));
     });
 
-    test('running with correct destination, skip 1 plugin', () async {
+    test('running with correct destination, exclude 1 plugin', () async {
       final Directory pluginDirectory1 =
           createFakePlugin('plugin1', packagesDir,
               withExtraFiles: <List<String>>[
@@ -151,11 +150,11 @@ void main() {
         'xctest',
         _kDestination,
         'foo_destination',
-        _kSkip,
+        '--exclude',
         'plugin1'
       ]);
 
-      expect(output, contains('plugin1 was skipped with the --skip flag.'));
+      expect(output, isNot(contains('Successfully ran xctest for plugin1')));
       expect(output, contains('Successfully ran xctest for plugin2'));
 
       expect(