ix Fix ix-tree click and toggle behavior

💡 What is the current behavior?

Tree items can only be expanded by clicking the toggle icon, not by clicking the item itself.
A click action is not emitted when clicking the area, where the toggle icon would be shown on an item that is not expandable.

GitHub Issue Number: #1633

The click action now is emitted when the area of an item is clicked, where the toggle icon would be shown if it was expandable.
An optional attribute to enable toggling items by clicking on the item itself was introduced.
The selection of an item remains when items are expanded or collapsed clicking the toggle icon.
Additional tests have been added.

A pull request can only be merged if all of these conditions are met (where applicable):

[ ] 🦮 Accessibility (a11y) features were implemented
[ ] 🗺️ Internationalization (i18n) - no hard coded strings
[ ] 📲 Responsiveness - components handle viewport changes and content overflow gracefully
[ ] 📄 Documentation was reviewed/updated (pnpm run docs)
[x] 🧪 Unit tests were added/updated and pass (pnpm test)
[ ] 📸 Visual regression tests were added/updated and pass (Guide)
[ ] 🧐 Static code analysis passes (pnpm lint)
[x] 🏗️ Successful compilation (pnpm build, changes pushed)