Standardize naming conventions in C code

[matapatos]

Standardize naming conventions in C code

Changes

• Add av_ prefix to all internal functions in validate_function.c:
  • transform_property_name → av_transform_property_name
  • get_property_name → av_get_property_name
  • get_property_value → av_get_property_value
  • add_field_error → av_add_field_error
  • validate_field_value → av_validate_field_value
• Standardize all functions to use zend_always_inline
• Update const correctness for error_message parameter
• Fix add_field_error to use ZVAL_STRINGL and remove redundant dtor
• Update all function calls to use new names
• Update header file declarations to match

Impact

• Consistent naming convention across the codebase
• Easier to identify extension-specific functions
• Improved code maintainability
• Better code organization

Closes #8