Use of undocumented `ArgumentParser` method breaking compatibility with newer Python versions

[matt-graham]

After installing the package in a Conda environment with Python 3.12 and attempting to run

swot_simulator --template conf.py

a TypeError is raised with traceback

Traceback (most recent call last):
  File "envs/swot_simulator/bin/swot_simulator", line 10, in <module>
    sys.exit(main())
             ^^^^^^
  File "envs/swot_simulator/lib/python3.12/site-packages/swot_simulator/launcher.py", line 459, in main
    args = usage()
           ^^^^^^^
  File "envs/swot_simulator/lib/python3.12/site-packages/swot_simulator/launcher.py", line 120, in usage
    namespace, _ = parser._parse_known_args(sys.argv[1:], namespace)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: ArgumentParser._parse_known_args() missing 1 required positional argument: 'intermixed'

This appears to be due to the call to the undocumented ArgumentParser._parse_known_args method in

swot_simulator/swot_simulator/cli/launcher.py

Line 110 in 8382703

namespace, _ = parser._parse_known_args(sys.argv[1:], namespace)

for which the interface has presumably change between the Python version the package was developed with and Python 3.12.