feat: Enhance MegaMenu with localization, caching, and new properties

- Added localization support for loading states, empty navigation, and submenu actions in both German and English.
- Introduced new properties in IMenuItem for description, openInNewWindow, and external links.
- Updated SPTermStorePickerService to handle cache versioning and language-specific caching.
- Implemented a new MegaMenuCore service for handling term properties, cache management, and navigation URL resolution.
- Refactored TaxonomyNavigationService to build menu hierarchy and filter hidden terms.
- Added automated tests for MegaMenu core functionalities and static asset validation.
- Removed unused ItemDictionary service.
- Created a comprehensive ToDo document outlining the implementation status and future tasks.

config/package-solution.json

@@ -3,7 +3,7 @@
   "solution": {
     "name": "mega-menu-client-side-solution",
     "id": "f4660e06-ce08-43ee-bfb7-5c4464e01133",
-    "version": "2.1.0.0",
+    "version": "2.2.0.0",
     "includeClientSideAssets": true,
     "skipFeatureDeployment": true
   },