python: test with more modern versions (#19452)

Python 3.12 has been released in October 2023, it should be tested in
the CI.

Python 3.7 is not maintained anymore, removing it from the minimum
required version in `pyproject.toml` files.

samples/openapi3/client/petstore/python-pydantic-v1-aiohttp/tests/util.py

@@ -1,19 +1,8 @@
 # flake8: noqa
 
-import asyncio
 import random
 
 
 def id_gen(bits=32):
     """ Returns a n-bit randomly generated int """
     return int(random.getrandbits(bits))
-
-
-def async_test(f):
-    def wrapper(*args, **kwargs):
-        # coro = asyncio.coroutine(f)
-        coro = f
-        future = coro(*args, **kwargs)
-        loop = asyncio.get_event_loop()
-        loop.run_until_complete(future)
-    return wrapper