[Enhancement](test) Add tests for Python UDF (apache#60499)

Some versions of pyarrow do not support directly converting Python's
`dict` type to the `arrow Map` type, so we need to manually convert the
`dict` type to a `list of tuple` before converting it to `arrow Map`
(consistent with the type mapping in `convert_arrow_field_to_python`).
```python
def convert_arrow_field_to_python(field, column_metadata=None):
      if pa.types.is_map(field.type):
          # pyarrow.lib.MapScalar's as_py() returns a list of tuples, convert to dict
          list_of_tuples = field.as_py()
          return dict(list_of_tuples) if list_of_tuples is not None else None
```

Author: linrrzqqq

be/src/runtime/user_function_cache.h

@@ -62,7 +62,9 @@ class UserFunctionCache {
     Status get_pypath(int64_t fid, const std::string& url, const std::string& checksum,
                       std::string* libpath);
 
+#ifndef BE_TEST
 private:
+#endif
     Status _load_cached_lib();
     Status _load_entry_from_lib(const std::string& dir, const std::string& file);
     Status _get_cache_entry(int64_t fid, const std::string& url, const std::string& checksum,

be/src/udf/python/python_server.py

@@ -373,6 +373,24 @@ def convert_python_to_arrow_value(value, output_type=None):
         else:
             # Not a struct type, treat as regular tuple and recurse without type
             return tuple(convert_python_to_arrow_value(v, None) for v in value)
+    
+    if isinstance(value, dict):
+        # For map types, convert keys and values recursively
+        if output_type and pa.types.is_map(output_type):
+            key_type = output_type.key_type
+            item_type = output_type.item_type
+            # Convert dict to list of tuples (PyArrow Map format)
+            converted_items = [
+                (convert_python_to_arrow_value(k, key_type),
+                convert_python_to_arrow_value(v, item_type))
+                for k, v in value.items()
+            ]
+            return converted_items
+        else:
+            # No type info, just recurse without type
+            return [(convert_python_to_arrow_value(k, None),
+                    convert_python_to_arrow_value(v, None))
+                    for k, v in value.items()]
 
     if isinstance(value, pd.Series):
         return value.apply(lambda v: convert_python_to_arrow_value(v, output_type))