[tools] Add column header for emulators information (#142853)

Add column information as table header for `flutter emulators` command.

**Before:**

```
2 available emulators:

Pixel_3_API_30   • Pixel 3 API 30   • Google • android
Resizable_API_33 • Resizable API 33 • Google • android

To run an emulator, run 'flutter emulators --launch <emulator id>'.
To create a new emulator, run 'flutter emulators --create [--name xyz]'.

You can find more information on managing emulators at the links below:
  https://developer.android.com/studio/run/managing-avds
  https://developer.android.com/studio/command-line/avdmanager
```

**After:**

```
2 available emulators:

Id               • Name             • Manufacturer • Platform

Pixel_3_API_30   • Pixel 3 API 30   • Google       • android
Resizable_API_33 • Resizable API 33 • Google       • android

To run an emulator, run 'flutter emulators --launch <emulator id>'.
To create a new emulator, run 'flutter emulators --create [--name xyz]'.

You can find more information on managing emulators at the links below:
  https://developer.android.com/studio/run/managing-avds
  https://developer.android.com/studio/command-line/avdmanager
```

fixes #140656

packages/flutter_tools/lib/src/emulator.dart

@@ -291,8 +291,16 @@ abstract class Emulator {
       return <String>[];
     }
 
+    const List<String> tableHeader = <String>[
+      'Id',
+      'Name',
+      'Manufacturer',
+      'Platform',
+    ];
+
     // Extract emulators information
     final List<List<String>> table = <List<String>>[
+      tableHeader,
       for (final Emulator emulator in emulators)
         <String>[
           emulator.id,
@@ -323,7 +331,10 @@ abstract class Emulator {
   }
 
   static void printEmulators(List<Emulator> emulators, Logger logger) {
-    descriptions(emulators).forEach(logger.printStatus);
+    final List<String> emulatorDescriptions = descriptions(emulators);
+    // Prints the first description as the table header, followed by a newline.
+    logger.printStatus('${emulatorDescriptions.first}\n');
+    emulatorDescriptions.sublist(1).forEach(logger.printStatus);
   }
 }
 

packages/flutter_tools/test/general.shard/emulator_test.dart

@@ -87,6 +87,18 @@ void main() {
         returnsNormally);
     });
 
+    testUsingContext('printEmulators prints the the emualtors information with header', () {
+      Emulator.printEmulators(emulators, testLogger);
+
+      expect(testLogger.statusText, '''
+Id                  • Name          • Manufacturer • Platform
+
+Nexus_5             • Nexus 5       • Google       • android
+Nexus_5X_API_27_x86 • Nexus 5X      • Google       • android
+iOS Simulator       • iOS Simulator • Apple        • android
+''');
+    });
+
     testUsingContext('getEmulators with no Android SDK', () async {
       // Test that EmulatorManager.getEmulators() doesn't throw when there's no Android SDK.
       final EmulatorManager emulatorManager = EmulatorManager(