Use new apptainer singularity install to avoid transient errors

[jo-basevi]

NCI have recently installed an Apptainer-based container engine on Gadi, which uses a different driver for mounting container image. In most cases it will require just swapping module load singularity with module load apptainer. This will hopefully fix the transient errors (see #26) and so far no errors have surfaced in my local testing. It could be good to get this change into at least payu/dev so it can be further tested.

Ben Menadue also picked up that the short-circuit to detect if running inside a container in the launcher scripts doesn't correctly detect Apptainer containers. They suggested a more reliable way would be to inspect that process's status directly:

$ cat /proc/self/status | grep NoNewPrivs | awk '{print $2}'
0

This will return 0 if running outside a container or 1 if inside. (Or more precisely, 0 if launching a container will work and 1 if it won't.)

So far in my tests, there hasn't been any "FATAL: container creation failed" using apptainer, so we could maybe also remove that retry logic when launching the container?