Improve schema-aware parsing for <xsd:any> to return structured dicts

[kaburagisec]

Summary

This PR enhances the Any.parse_xmlelements() method to improve the deserialization of <xsd:any> elements by using schema-based type resolution where available. When child elements are found, the method attempts to:

• Look up each child element using the provided schema
• Deserialize them into nested Python dictionaries keyed by tag name
• Fall back to text content or the raw lxml Element if schema resolution fails

What Changed

• Rewrote zeep.xsd.elements.Any.parse_xmlelements() to return structured dict instead of list of raw elements
• Supports nested parsing of child elements
• Improved docstring to match behavior

Why

Helps improve parsing of <xsd:any> blocks in extensible XML schemas. Common in many real-world SOAP APIs.

Backward Compatibility

• Compatible with current Zeep API
• Falls back safely if schema lookup fails

Related Issues

• Fixes Garbage in nested datatypes #918
• Fixes Zeep returned empty array #582
• Fixes The "Extension" part at ONVIF wsdl is always parsed into a weird dict #1472

Let me know if you want me to add tests or make this opt-in via setting.