Fix #2

[OsamaAlRashed]

This PR fixes several issues with the GridazorDropdown component and adds better support for dependent dropdowns:

Key Changes:

1. Fixed valueFormatter:

   • Added proper handling for cases where cellEditorParams is a function
   • Improved handling of null/undefined values
   • More robust text lookup for display values

2. Enhanced Remote Data Handling:

   • Preserved original searchUrl structure but improved request handling
   • Added better error handling for network requests
   • Added missing UI feedback for "no results" state

3. Added Dependent Field Support:

   • Added resetDependentValue helper to properly handle parent-child relationships
   • When a parent field (e.g., category) changes, the child field (e.g., subcategory) is now automatically reset to null
   • Cell UI is properly refreshed to show the change immediately

4. Code Organization:

   • Created a more robust gridazorDropdownHelper object that centralizes common functionality
   • Improved reusability of components

These changes ensure proper handling of dropdown dependency scenarios like the Category → Subcategory relationship, preventing invalid data states where a subcategory might remain selected even when it doesn't belong to the newly selected parent category.