[messages] Sort analyzer_messages.dart.

Sorts declarartions in the file
`pkg/analyzer_utilities/lib/analyzer_messages.dart`. The files in this
package are not yet checked by `verify_sorted_test.dart`, so I failed
to notice when I introduced a sorting error.

In a follow-up CL, I will update `verify_sorted_test.dart` to verify
sorting in `pkg/analyzer_utilities`, so that this doesn't happen
again.

Change-Id: I6a6a6964542065c7894499394b74269152a64853
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/458460
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

pkg/analyzer_utilities/lib/analyzer_messages.dart

@@ -16,10 +16,6 @@ const codesFile = GeneratedDiagnosticFile(
   parentLibrary: 'package:analyzer/src/error/codes.dart',
 );
 
-/// Enum representing the packages into which analyzer diagnostics can be
-/// generated.
-enum AnalyzerDiagnosticPackage { analyzer, analysisServer, linter }
-
 /// Information about all the classes derived from `DiagnosticCode` that are
 /// code-generated based on the contents of the analyzer and front end
 /// `messages.yaml` files.
@@ -319,6 +315,10 @@ class AliasMessage extends AnalyzerMessage {
   }
 }
 
+/// Enum representing the packages into which analyzer diagnostics can be
+/// generated.
+enum AnalyzerDiagnosticPackage { analyzer, analysisServer, linter }
+
 /// In-memory representation of diagnostic information obtained from the
 /// analyzer's `messages.yaml` file.
 class AnalyzerMessage extends Message with MessageWithAnalyzerCode {