Update some Focus docs (#87561)

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

@@ -309,11 +309,12 @@ enum UnfocusDisposition {
 /// The [FocusManager] receives key events from [RawKeyboard] and
 /// [HardwareKeyboard] and will pass them to the focused nodes. It starts with
 /// the node with the primary focus, and will call the [onKey] or [onKeyEvent]
-/// callback for that node. If the callback returns false, indicating that it did
-/// not handle the event, the [FocusManager] will move to the parent of that node
-/// and call its [onKey] or [onKeyEvent]. If that [onKey] or [onKeyEvent] returns
-/// true, then it will stop propagating the event. If it reaches the root
-/// [FocusScopeNode], [FocusManager.rootScope], the event is discarded.
+/// callback for that node. If the callback returns [KeyEventResult.ignored],
+/// indicating that it did not handle the event, the [FocusManager] will move
+/// to the parent of that node and call its [onKey] or [onKeyEvent]. If that
+/// [onKey] or [onKeyEvent] returns [KeyEventResult.handled], then it will stop
+/// propagating the event. If it reaches the root [FocusScopeNode],
+/// [FocusManager.rootScope], the event is discarded.
 /// {@endtemplate}
 ///
 /// ## Focus Traversal

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

@@ -16,7 +16,7 @@ import 'inherited_notifier.dart';
 ///
 /// For keyboard events, [onKey] is called if [FocusNode.hasFocus] is true for
 /// this widget's [focusNode], unless a focused descendant's [onKey] callback
-/// returns true when called.
+/// returns [KeyEventResult.handled] when called.
 ///
 /// This widget does not provide any visual indication that the focus has
 /// changed. Any desired visual changes should be made when [onFocusChange] is
@@ -316,9 +316,9 @@ class Focus extends StatefulWidget {
   /// focus.
   ///
   /// Key events are first given to the [FocusNode] that has primary focus, and
-  /// if its [onKeyEvent] method return false, then they are given to each
-  /// ancestor node up the focus hierarchy in turn. If an event reaches the root
-  /// of the hierarchy, it is discarded.
+  /// if its [onKeyEvent] method returns [KeyEventResult.ignored], then they are
+  /// given to each ancestor node up the focus hierarchy in turn. If an event
+  /// reaches the root of the hierarchy, it is discarded.
   ///
   /// This is not the way to get text input in the manner of a text field: it
   /// leaves out support for input method editors, and doesn't support soft
@@ -742,8 +742,9 @@ class _FocusState extends State<Focus> {
 /// The [onKey] argument allows specification of a key event handler that is
 /// invoked when this node or one of its children has focus. Keys are handed to
 /// the primary focused widget first, and then they propagate through the
-/// ancestors of that node, stopping if one of them returns true from [onKey],
-/// indicating that it has handled the event.
+/// ancestors of that node, stopping if one of them returns
+/// [KeyEventResult.handled] from [onKey], indicating that it has handled the
+/// event.
 ///
 /// Managing a [FocusScopeNode] means managing its lifecycle, listening for
 /// changes in focus, and re-parenting it when needed to keep the focus