Remove outdated Fuchsia concepts (#107335)

Fuchsia will soon remove all support for Component Framework version 1
components (recognized by component manifests ending in `.cmx`).
Notably, some of the `flutter` tool commands for Fuchsia devices--
notably, but not limited to, those related to CFv1--are outdated, and
either do not work today or soon won't work.

This PR removes the outdated components and commands, replacing some
with the newer version, or simply removing the non-working features,
in some cases.

Author: richkadel

dev/benchmarks/complex_layout/fuchsia/meta/complex_layout.cmx

@@ -14,7 +14,6 @@ import 'build_aar.dart';
 import 'build_apk.dart';
 import 'build_appbundle.dart';
 import 'build_bundle.dart';
-import 'build_fuchsia.dart';
 import 'build_ios.dart';
 import 'build_ios_framework.dart';
 import 'build_macos_framework.dart';
@@ -43,7 +42,6 @@ class BuildCommand extends FlutterCommand {
       verboseHelp: verboseHelp
     ));
     _addSubcommand(BuildWindowsCommand(verboseHelp: verboseHelp));
-    _addSubcommand(BuildFuchsiaCommand(verboseHelp: verboseHelp));
   }
 
   void _addSubcommand(BuildSubCommand command) {
@@ -83,8 +81,11 @@ abstract class BuildSubCommand extends FlutterCommand {
   @protected
   void displayNullSafetyMode(BuildInfo buildInfo) {
     globals.printStatus('');
-    if (buildInfo.nullSafetyMode ==  NullSafetyMode.sound) {
-      globals.printStatus('💪 Building with sound null safety 💪', emphasis: true);
+    if (buildInfo.nullSafetyMode == NullSafetyMode.sound) {
+      globals.printStatus(
+        '💪 Building with sound null safety 💪',
+        emphasis: true,
+      );
     } else {
       globals.printStatus(
         'Building without sound null safety',