Allow find.byTooltip to use a RegEx (#149348)

## Description

This adds the ability for `find.byTooltip` to use a `RegEx` to match the tooltip.

Also, adds some tests for `byTooltip`, since there weren't any.

## Tests
 - added tests

packages/flutter_test/lib/src/finders.dart

@@ -365,13 +365,20 @@ class CommonFinders {
   ///
   /// ```dart
   /// expect(find.byTooltip('Back'), findsOneWidget);
+  /// expect(find.byTooltip(RegExp('Back.*')), findsNWidgets(2));
   /// ```
   ///
   /// If the `skipOffstage` argument is true (the default), then this skips
   /// nodes that are [Offstage] or that are from inactive [Route]s.
-  Finder byTooltip(String message, { bool skipOffstage = true }) {
+  Finder byTooltip(Pattern message, {bool skipOffstage = true}) {
     return byWidgetPredicate(
-      (Widget widget) => widget is Tooltip && widget.message == message,
+      (Widget widget) {
+        return widget is Tooltip &&
+            (message is RegExp
+                ? ((widget.message != null && message.hasMatch(widget.message!)) ||
+                    (widget.richMessage != null && message.hasMatch(widget.richMessage!.toPlainText())))
+                : ((widget.message ?? widget.richMessage?.toPlainText()) == message));
+      },
       skipOffstage: skipOffstage,
     );
   }

packages/flutter_test/test/finders_test.dart

@@ -301,6 +301,98 @@ void main() {
     });
   });
 
+  group('byTooltip', () {
+    testWidgets('finds widgets by tooltip', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          message: 'Tooltip Message',
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip('Tooltip Message'), findsOneWidget);
+    });
+
+    testWidgets('finds widgets with tooltip by RegExp', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          message: 'Tooltip Message',
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip('Tooltip'), findsNothing);
+      expect(find.byTooltip(RegExp(r'^Tooltip')), findsOneWidget);
+    });
+
+    testWidgets('finds widgets by rich text tooltip', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          richMessage: TextSpan(
+            children: <InlineSpan>[
+            TextSpan(text: 'Tooltip '),
+            TextSpan(text: 'Message'),
+          ]),
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip('Tooltip Message'), findsOneWidget);
+    });
+
+    testWidgets('finds widgets with rich text tooltip by RegExp', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          richMessage: TextSpan(
+            children: <InlineSpan>[
+            TextSpan(text: 'Tooltip '),
+            TextSpan(text: 'Message'),
+          ]),
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip('Tooltip M'), findsNothing);
+      expect(find.byTooltip(RegExp(r'^Tooltip M')), findsOneWidget);
+    });
+
+    testWidgets('finds empty string with tooltip', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          message: '',
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip(''), findsOneWidget);
+
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          richMessage: TextSpan(
+            children: <InlineSpan>[
+            TextSpan(text: ''),
+          ]),
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip(''), findsOneWidget);
+
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          message: '',
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip(RegExp(r'^$')), findsOneWidget);
+
+      await tester.pumpWidget(_boilerplate(
+        const Tooltip(
+          richMessage: TextSpan(
+            children: <InlineSpan>[
+            TextSpan(text: ''),
+          ]),
+          child: Text('+'),
+        ),
+      ));
+      expect(find.byTooltip(RegExp(r'^$')), findsOneWidget);
+    });
+  });
+
   group('hitTestable', () {
     testWidgets('excludes non-hit-testable widgets',
         (WidgetTester tester) async {
@@ -1356,10 +1448,17 @@ void main() {
 Widget _boilerplate(Widget child) {
   return Directionality(
     textDirection: TextDirection.ltr,
-    child: child,
+    child: Navigator(
+      onGenerateRoute: (RouteSettings settings) {
+        return MaterialPageRoute<void>(
+          builder: (BuildContext context) => child,
+        );
+      },
+    ),
   );
 }
 
+
 class SimpleCustomSemanticsWidget extends LeafRenderObjectWidget {
   const SimpleCustomSemanticsWidget(this.label, {super.key});