Use IntEnum instead of Enum for enum class wrappers (#222)

Change the generated Python enum wrappers to inherit from IntEnum
instead of Enum. This fixes a bug where set parameters containing
enum class values would fail with "TypeError: an integer is required"
when iterating.

The issue was that:
1. Generated code declares `cdef int item0` for iteration
2. But iterating over a set of Enum values yields Enum objects, not ints
3. Cython cannot assign an Enum object to `cdef int`

With IntEnum:
- Enum values ARE integers (isinstance(val, int) is True)
- Cython's `cdef int` can directly accept IntEnum values
- Round-trip operations (get → set) work correctly
- Backwards compatible with code expecting integers

Tested with pyOpenMS which uses `cdef enum class ActivationMethod`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: timosachsenberg

autowrap/CodeGenerator.py

@@ -348,7 +348,7 @@ def create_for(
 
         pyi_code = "from __future__ import annotations\n"
         pyi_code += "from typing import overload, Any, List, Dict, Tuple, Set, Sequence, Union\n\n"
-        pyi_code += "from enum import Enum as _PyEnum\n\n"
+        pyi_code += "from enum import IntEnum as _PyEnum\n\n"
         pyi_code += "\n".join(ci.render() for ci in self.top_level_typestub_code)
         pyi_code += "\n\n"
         for n, c in self.typestub_codes.items():
@@ -2040,7 +2040,7 @@ def create_default_cimports(self):
                    |#Generated with autowrap %s and Cython (Parser) %s
                    |#cython: c_string_encoding=ascii
                    |#cython: embedsignature=False
-                   |from  enum            import Enum as _PyEnum
+                   |from  enum            import IntEnum as _PyEnum
                    |from  cpython         cimport Py_buffer
                    |from  cpython         cimport bool as pybool_t
                    |from  libcpp.string   cimport string as libcpp_string