Add support for managing Ironic baremetal port groups.
Include CI role coverage and unit tests for create, update, delete, and check mode behavior.
Add a reno fragment describing the new module.
Tests-Run: python -m pytest tests/unit/modules/cloud/openstack/test_baremetal_port_group.py
Change-Id: I98564fcb5b81a1dd7be1fbf5ffca364483296655
