[Breaking Change] Accessibility focus traversal order of tooltip changed

[Longcatis Looong]

The accessibility traversal order of the Tooltip widget was changed in https://github.com/flutter/flutter/pull/134921. When the Tooltip message is visible, it is now visited immediately after `Tooltip.child` during accessibility focus traversal. See https://github.com/flutter/website/pull/9469 for an example of how this change affects the semantics tree.

If you are seeing accessibility test failures caused by the tooltip message changing location in the tree, consider updating the failing test to adopt the new behavior.