Incompatible with nanobind 2.2 on Py3.12

[inducer]

As pointed out by @matthiasdiener in #788.

Example:

Traceback (most recent call last):
  File "/home/andreas/src/pyopencl/examples/demo.py", line 29, in <module>
    knl = prg.sum  # Use this Kernel object for repeated calls
          ^^^^^^^
  File "/home/andreas/src/env-3.12/lib/python3.12/site-packages/pyopencl/__init__.py", line 443, in __getattr__
    knl = Kernel(self, attr)
          ^^^^^^^^^^^^^^^^^^
TypeError: __init__(): incompatible function arguments. The following argument types are supported:
    1. __init__(self, arg0: pyopencl._cl._Program, arg1: str, /) -> None

Invoked with types: pyopencl._cl.Kernel, pyopencl.Program, str

We'll probably need to avoid overriding __init__ the way we have. The easiest way to do this may be to just port the existing constructors to C++.

[matthiasdiener]

Unfortunately, a simple reproducer does not appear to show the same issue:

cmake_minimum_required(VERSION 3.15...3.27)
project(my_project) # Replace 'my_project' with the name of your project

if (CMAKE_VERSION VERSION_LESS 3.18)
  set(DEV_MODULE Development)
else()
  set(DEV_MODULE Development.Module)
endif()

find_package(Python 3.8 COMPONENTS Interpreter ${DEV_MODULE} REQUIRED)

if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
    set(CMAKE_BUILD_TYPE Release CACHE STRING "Choose the type of build." FORCE)
    set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
endif()

execute_process(
    COMMAND "${Python_EXECUTABLE}" -m nanobind --cmake_dir
    OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE nanobind_ROOT)
find_package(nanobind CONFIG REQUIRED)

nanobind_add_module(my_ext my_ext.cpp)

#include <nanobind/nanobind.h>
#include <iostream>

struct MyType {
    MyType() {}};

NB_MODULE(my_ext, m) {
    nanobind::class_<MyType>(m, "MyType", nanobind::dynamic_attr())
        .def("__init__",
                [](MyType *t, int bar)
                {
                    std::cout << "C++ __init__ " << bar << std::endl;
                    new (t) MyType();
                });
}

from my_ext import MyType

def my_init(self, s:str):  # different arg type compared to C++
    print("python __init__", s)

MyType.__init__ = my_init

MyType(42)
MyType("foo")

$ python t.py
python __init__ 42
python __init__ foo

Edit: Turns out this is specific to Python 3.12; with that version, the reproducer above shows the issue.