Change xcodebuild to be a "slow operation" (#61518)

The Xcode build almost always takes longer than 2 seconds. With the
operation classified as a "fast operation", the Flutter tool will
warn the user that the build is "taking an unexpectedly long time".
This updates the operation to be a "slow operation", which will only
warn the user if it takes 2+ minutes.

packages/flutter_tools/lib/src/ios/mac.dart

@@ -320,7 +320,7 @@ Future<XcodeBuildResult> buildXcodeProject({
   buildCommands.addAll(environmentVariablesAsXcodeBuildSettings(globals.platform));
 
   final Stopwatch sw = Stopwatch()..start();
-  initialBuildStatus = globals.logger.startProgress('Running Xcode build...', timeout: timeoutConfiguration.fastOperation);
+  initialBuildStatus = globals.logger.startProgress('Running Xcode build...', timeout: timeoutConfiguration.slowOperation);
 
   final RunResult buildResult = await _runBuildWithRetries(buildCommands, app);