Reveal cursor on panel expand

@peterflynn Simple fix for issue #3003, and (nearly) identical to closed and outdated pull request #3931.
Yeah, this breaks the way hints are passed in via `_notifyLayoutChange()`, which in turn comes from `EditorManager._doShow()`.  Either need to change that call site or preserve the old signature of `triggerEditorResize()` where this arg is a flag (and add a 2nd arg for the other flag).  If changing the signature, should rename similar to my `_onEditorAreaResize()` comment above.