Move the requestKeyboard up to the widgets layer (#141655)

Turns out all implementations of this method made this call, so it seems like it should belong in the superclass.

packages/flutter/lib/src/cupertino/text_field.dart

@@ -117,7 +117,6 @@ class _CupertinoTextFieldSelectionGestureDetectorBuilder extends TextSelectionGe
       }
     }
     super.onSingleTapUp(details);
-    _state._requestKeyboard();
     _state.widget.onTap?.call();
   }
 

packages/flutter/lib/src/material/text_field.dart

@@ -65,12 +65,6 @@ class _TextFieldSelectionGestureDetectorBuilder extends TextSelectionGestureDete
     // Not required.
   }
 
-  @override
-  void onSingleTapUp(TapDragUpDetails details) {
-    super.onSingleTapUp(details);
-    _state._requestKeyboard();
-  }
-
   @override
   bool get onUserTapAlwaysCalled => _state.widget.onTapAlwaysCalled;
 

packages/flutter/lib/src/widgets/text_selection.dart

@@ -2417,6 +2417,7 @@ class TextSelectionGestureDetectorBuilder {
           }
       }
     }
+    editableText.requestKeyboard();
   }
 
   /// Handler for [TextSelectionGestureDetector.onSingleTapCancel].