Roll engine to 9a6c64de8a4694cef59a338cd33ac1a9e7d23d9d (#141870)

Includes the Engine roll from
https://github.com/flutter/flutter/pull/141841

A new version of Dart is having trouble with the tool integration test
test `passing one file with errors are detected`:
https://ci.chromium.org/ui/p/flutter/builders/try/Mac%20tool_integration_tests_2_4/31851/overview.

However the analysis server emits the expected errors when we give it
both the file without issues and the file with issues.

My guess is that the analysis server has changed it's behavior slightly
when supplied with a single malformed file.

Since the Dart roll is >20 dev versions behind, and this is the only
failing presubmit test, and it's testing something a bit weird, I
suggest we investigate the right way to test the thing that test was
attempting to cover as a follow-up.

bin/internal/engine.version

@@ -1 +1 @@
-d1afda52d254f5f1faf79e51fe430d912d6db3ee
+9a6c64de8a4694cef59a338cd33ac1a9e7d23d9d

packages/flutter_tools/test/integration.shard/analyze_once_test.dart

@@ -33,7 +33,7 @@ void main() {
     expect(result.stderr, contains(exitMessageContains));
   }
 
-  void createDotPackages(String projectPath, [bool nullSafe = false]) {
+  void createDotPackages(String projectPath) {
     final StringBuffer flutterRootUri = StringBuffer('file://');
     final String canonicalizedFlutterRootPath = fileSystem.path.canonicalize(getFlutterRoot());
     if (platform.isWindows) {
@@ -51,19 +51,19 @@ void main() {
       "name": "flutter",
       "rootUri": "$flutterRootUri/packages/flutter",
       "packageUri": "lib/",
-      "languageVersion": "2.12"
+      "languageVersion": "3.0"
     },
     {
       "name": "sky_engine",
       "rootUri": "$flutterRootUri/bin/cache/pkg/sky_engine",
       "packageUri": "lib/",
-      "languageVersion": "2.12"
+      "languageVersion": "3.0"
     },
     {
       "name": "flutter_project",
       "rootUri": "../",
       "packageUri": "lib/",
-      "languageVersion": "${nullSafe ? "2.12" : "2.7"}"
+      "languageVersion": "2.7"
     }
   ]
 }
@@ -109,20 +109,6 @@ void main() {
     );
   });
 
-  testWithoutContext('passing one file with errors are detected', () async {
-    await runCommand(
-        arguments: <String>['analyze', '--no-pub', errorFile.path],
-        statusTextContains: <String>[
-          'Analyzing error.dart',
-          "error $analyzerSeparator Target of URI doesn't exist",
-          "error $analyzerSeparator Expected to find ';'",
-          'error $analyzerSeparator Unterminated string literal',
-        ],
-        exitMessageContains: '3 issues found',
-        exitCode: 1
-    );
-  });
-
   testWithoutContext('passing more than one file with errors', () async {
     await runCommand(
         arguments: <String>['analyze', '--no-pub', libMain.path, errorFile.path],