refactor!: Upgrade to Vaadin 25

[vursen]

1. ParentItemProvider has been removed, as the HierarchicalDataProvider interface now officially supports the getParent method. The only difference is that it's now expected to return null if the item doesn't have a parent, instead of an Optional:

   - public Optional<Department> getParent(Department item) {
   + public Department getParent(Department item) {

2. The scrollToItem feature has been removed from this addon, as it's now built into Vaadin's official TreeGrid component. Depending on the data provider type, it may require implementing HierarchicalDataProvider#getParent or/and HierarchicalDataProvider#getItemIndex:

   DataProvider	isInMemory()	getItemIndex()	getParent()
   TreeDataProvider	true	not required	not required
   HierarchicalDataProvider	true	not required	required
   HierarchicalDataProvider	false	required	required

   When using in-memory hierarchical data providers, getParent() is still the only required method, however.

[vursen]

The scrollToItem feature is now part of TreeGrid.

[web-padawan]

LGTM, tested the demo and everything seems to work.

[web-padawan]

nit: could also update static get version() above.

[vursen]

Thanks, done.

[vursen]

This PR should also fix:

• _selectionGridSelectRowWithItem(e, item, index) will send the wrong index when TR index is not the index of the clicked item #64
• Scroll to item not working as expected Vadin 24.1.4 / Selection tree grid 3.0.1 #43
• ScrollToItem corrupts tree data #53