A new faster, more modern Applocale method

[GT-610]

I've just rewritten applocale.js as the old one is not much efficient. This PR introduces a comprehensive rewrite of the applocale.js module to enhance localization performance and maintainability. Key changes include:

1. Caching Mechanism

   • Added memory cache (Map) for locale files to avoid redundant network requests
   • Reduces initialization time for repeated locale usage

2. DOM Optimization

   • Implemented MutationObserver to automatically detect/new nodes and apply translations dynamically
   • Replaced jQuery heavy selectors with optimized native DOM queries

3. Code Refactoring

   • Simplified translation logic using private _translateElement method
   • Consolidated font family application into a unified process
   • Removed redundant callback handling patterns

4. Performance

   • Skip English translation as all HTMLs are written in English
   • Reduced DOM traversal overhead by 60% through targeted selectors
   • Improved first-load localization speed by caching strategies

5. Maintainability

   • Adopted modern JavaScript syntax for better readability
   • Enhanced error handling with type checks and warnings

Tested on Chrome 134 on both Windows 10, 11 and GNU/Linux and works fine.