Add more container dependency checks in run_sorter

[JoeZiminski]

This PR closes #2855 by adding in additional checks on container and GPU dependencies when running run_sorter().

It adds checks that docker or singularity are installed (if running sorter with docker or singularity respectively) and also that the corresponding python packages docker and spython are installed. It also show a warning if, on Linux, some nvidia-docker tools are not available, which are usually necessary. See #2855 for a disucssion, but these nvidia-docker dependencies are a little complex so instead of raising an error, only a warning is shown.

I tested all locally and they work okay. It is not easy to test these nvidia-docker checks in code and so have left these, they raise only a warning anyway. The tests are a little bit 'extra', in particulary testing has_docker_python() and has_spython(). This patches sys.module to pretend like these modules are not available, then checks these has_<dependency> functions return False. However, these tests are a little bit complex and add a reasonable amount of code to check what is basically a try/except function so although it's nice to test as much as possible, would be happy to remove if the maintenance burden is too high.

The other tests check that at runtime, run_sorter raises the appropriate error when the has_<dependency> functions return False. This is achieved by 'monkeypatching' these has_<dependency> functions so they return False at runtime. Then it can be checked that run_sorter is raising the correct error. I think these tests are more valuable, are less complex that the tests discussed above.

[zm711]

couple typos.

[JoeZiminski]

Thanks @alejoe91 and @zm711! @alejoe91 thanks for the apptainer addition, I wanted to test this locally but I have completely KO-d my linux parition by messing around with GPU drivers and it no longer boots 😆. So I can't physically check it with singularity / apptainer installed / not installed but checked the code carefully and command looks good and I'm happy to proceed with merging. Cheers!

[zm711]

This looks good to me, but since I almost never use the containers I will leave it to @alejoe91 for the review for correctness.

[samuelgarcia]

This looks perfect to me.
Thanks a lot for sanitazing this zone, this will be extremenlly helpfull for user fightinh with installation.