migrate the package_autoroller from querying by label to title (#128066)

Fixes https://github.com/flutter/flutter/issues/128067

dev/conductor/core/lib/src/packages_autoroller.dart

@@ -50,9 +50,11 @@ class PackageAutoroller {
 
   static const String hostname = 'github.com';
 
-  static const String prBody = '''
-This PR was generated by `flutter update-packages --force-upgrade`.
-''';
+  String get prBody {
+    return '''
+This PR was generated by the automated
+[Pub packages autoroller](https://github.com/flutter/flutter/blob/main/dev/conductor/core/bin/packages_autoroller.dart).''';
+  }
 
   /// Name of the feature branch to be opened on against the mirror repo.
   ///
@@ -166,12 +168,13 @@ This PR was generated by `flutter update-packages --force-upgrade`.
     );
   }
 
+  static const String _prTitle = 'Roll pub packages';
+
   /// Create a pull request on GitHub.
   ///
   /// Depends on the gh cli tool.
   Future<void> createPr({
     required io.Directory repository,
-    String title = 'Roll pub packages',
     String body = 'This PR was generated by `flutter update-packages --force-upgrade`.',
     String base = FrameworkRepository.defaultBranch,
     bool draft = false,
@@ -185,7 +188,7 @@ This PR was generated by `flutter update-packages --force-upgrade`.
         'pr',
         'create',
         '--title',
-        title.trim(),
+        _prTitle,
         '--body',
         body.trim(),
         '--head',
@@ -257,15 +260,19 @@ This PR was generated by `flutter update-packages --force-upgrade`.
     final String openPrString = await cli(<String>[
       'pr',
       'list',
+
       '--author',
       githubUsername,
+
       '--repo',
       'flutter/flutter',
+
       '--state',
       'open',
-      // We are only interested in pub rolls, not devicelab flaky PRs
-      '--label',
-      'tool',
+
+      '--search',
+      _prTitle,
+
       // Return structured JSON with the PR numbers of open PRs
       '--json',
       'number',
@@ -274,6 +281,7 @@ This PR was generated by `flutter update-packages --force-upgrade`.
     // This will be an array of objects, one for each open PR.
     final List<Object?> openPrs = json.decode(openPrString) as List<Object?>;
 
+    // We are only interested in pub rolls, not devicelab flaky PRs
     if (openPrs.isNotEmpty) {
       log('$githubUsername already has open tool PRs:\n$openPrs');
       return true;

dev/conductor/core/test/packages_autoroller_test.dart

@@ -204,8 +204,8 @@ void main() {
         'flutter/flutter',
         '--state',
         'open',
-        '--label',
-        'tool',
+        '--search',
+        'Roll pub packages',
         '--json',
         'number',
       // Non empty array means there are open PRs by the bot with the tool label
@@ -244,8 +244,8 @@ void main() {
         'flutter/flutter',
         '--state',
         'open',
-        '--label',
-        'tool',
+        '--search',
+        'Roll pub packages',
         '--json',
         'number',
       // Returns empty array, as there are no other open roll PRs from the bot
@@ -340,8 +340,8 @@ void main() {
         'flutter/flutter',
         '--state',
         'open',
-        '--label',
-        'tool',
+        '--search',
+        'Roll pub packages',
         '--json',
         'number',
       // Returns empty array, as there are no other open roll PRs from the bot