Make setup rundir more robust take #2

[ashjbarnes]

This is a clone of #177 with three cherry picked commits. The other PR got really messy as @angus-g needed to handle the update to numpy 2 in between

[angus-g]

There's nothing wrong with force pushing to your PR branches. You could've essentially just pushed this branch to the one for #177. :)

[ashjbarnes]

In this PR I gave up on changing structure to move the demos folder to regional-mom6, because it required altering the pyproject.toml and then troubleshooting the github workflow file. To implement this in line wiht conda guidelines (see Angus' comment ) this will take a bit more fiddling around, and another PR.

What we have in this PR means that there's extra error handling when the CPU layout isn't provided, and the setup_rundir function looks at the package root folder for the premade_run_directories if it can't find the folder where it expects it, in the case that the user is being lazy and importing it directly for development purposes.

[ashjbarnes]

There's nothing wrong with force pushing to your PR branches. You could've essentially just pushed this branch to the one for #177. :)

Oh thanks good to know! I thought I'd made a huge mess of the other one by force pushing like 4 times either side of your numpy PR