Pin apptainer version used in Github Actions CI pipelines and re-enable tests using apptainer.

[wholtz]

This repo's tests that utilize Apptainer started failing around the time v1.4.3 of Apptainer was released. We were not pinning the version of Apptainer within our Github Actions configuration. We may have been hitting a bug in v1.4.3 of Apptainer.

I would like to re-enable the Apptainer tests. Ideally this will involved pinning the version of Apptainer installed.