Extract google maps loader to service

[JulienVannier66]

What does this PR do?

This PR extracts the Google Maps loader logic from the setup-autocomplete modifier into a dedicated autocomplete-handler service, improving testability and separation of concerns.

Key changes:

• Created AutocompleteHandlerService that centralizes Google Maps loader instantiation
• Removed the loader parameter from setup-autocomplete modifier (now injected via service)
• Added AutocompleteHandlerServiceMock for testing with MockLoader
• Updated all tests to register the mock service instead of passing the loader directly
• Added unit tests for both production and test service implementations

What are the observable changes?

🧑‍💻 Developer Heads Up

⚡ Since we are using Ember Octane now:

• Feel free to migrate existing components to Glimmer Components.
• Write new ones exclusively in it.

Useful Resource : Ember Octane vs Classic Cheat Sheet

Good PR checklist

• Title makes sense
• Is against the correct branch
• Only addresses one issue
• Properly assigned
• Added/updated tests
• Added/updated documentation
• Migrated touched components to Glimmer Components
• Properly labeled

[linear]

VEL-7196 Extract Google Maps Loader to AutocompleteHandler Service