conda: update lockfiles, resolve issues with Singularity images

This merge request incorporates two changes, both related to gstlal conda environments and the Docker images generated from these environments:

1. Update lockfiles

This updates the (rather old) conda environments to the latest lalsuite + ligo-lw versions, which resolves issues due to missing executables (ligolw_run_sqlite, for example).

2. Resolve conda issues with Singularity images.

This fixes issues when running commands in Singularity containers generated from the published conda Docker images in this repo's container registry. Conda + Singularity has been a pain to deal with, and one particular issue that this solves is when trying to execute commands with singularity exec. Because conda environments require activation before they can be used, you can define a Docker entrypoint which effectively does all the work. The problem? singularity exec bypasses this intentionally/

This resolves this particular issue by explicitly pointing at the right python interpreter in executables, as well as adding all the installed executables into $PATH, effectively bypassing the problem.

This also fixes the remaining issues in the CI.