Deprecation: nesting argument groups

[pawamoy]

• I have searched the issue tracker and believe that this is not a duplicate.

Nesting argument groups seems to be deprecated, starting at Python 3.11.

Steps to reproduce

Simply run PDM with deprecation warnings enabled.

Actual behavior

From pytest output:

  ___________________________________________________________________________________________ test_multirun ____________________________________________________________________________________________
  [gw0] linux -- Python 3.11.0 /home/pawamoy/.basher-packages/pyenv/pyenv/versions/3.11.0/bin/python3.11

      def test_multirun() -> None:
          """Basic run."""
  >       main(["multirun", "python", "-V"])

  tests/test_plugin.py:8: 
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
  __pypackages__/3.11/lib/pdm/core.py:289: in main
      return Core().main(args)
  __pypackages__/3.11/lib/pdm/core.py:57: in __init__
      self.init_parser()
  __pypackages__/3.11/lib/pdm/core.py:93: in init_parser
      self.register_command(klass, klass.name or name)
  __pypackages__/3.11/lib/pdm/core.py:232: in register_command
      command.register_to(self.subparsers, name)
  __pypackages__/3.11/lib/pdm/cli/commands/base.py:44: in register_to
      command = cls(parser)
  __pypackages__/3.11/lib/pdm/cli/commands/base.py:25: in __init__
      self.add_arguments(parser)
  __pypackages__/3.11/lib/pdm/cli/commands/run.py:354: in add_arguments
      exec = action.add_argument_group("execution", "Execution parameters")
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

  self = <argparse._MutuallyExclusiveGroup object at 0x7fb3d80b9690>, args = ('execution', 'Execution parameters'), kwargs = {}

      def add_argument_group(self, *args, **kwargs):
  >       warnings.warn(
              "Nesting argument groups is deprecated.",
              category=DeprecationWarning,
              stacklevel=2
          )
  E       DeprecationWarning: Nesting argument groups is deprecated.

Expected behavior

The code should be updated to avoid the deprecated nested groups.
I'll ignore the warning in the meantime 🙂

Environment Information

# Paste the output of `pdm info && pdm info --env` below:
PDM version:
  2.7.0
Python Interpreter:
  /home/pawamoy/.basher-packages/pyenv/pyenv/versions/3.11.0/bin/python3 (3.11)
Project Root:
  /media/data/dev/pdm-multirun
Local Packages:
  /media/data/dev/pdm-multirun/__pypackages__/3.11
{
  "implementation_name": "cpython",
  "implementation_version": "3.11.0",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "6.3.6-arch1-1",
  "platform_system": "Linux",
  "platform_version": "#1 SMP PREEMPT_DYNAMIC Mon, 05 Jun 2023 15:12:57 +0000",
  "python_full_version": "3.11.0",
  "platform_python_implementation": "CPython",
  "python_version": "3.11",
  "sys_platform": "linux"
}