Implement priority, completion threshold percentage and user comment into AProds

This is a first run at adding functionality to allow for per-job priorities and completion thresholds and per-production user comments.

I aim to enable:

• Taking these new fields from a parsed yaml to create a job with the relevant columns set to the correct values.
• At the production creation stage set the priority of each job to its value according to the yaml.
• At the JIRA submission stage add a new column corresponding to the per-job completion threshold into the summary table, and print the user comment before the cc list.

Requires lbapcommon!23 (merged).

More in addressing procedures and rules, see DPA task https://gitlab.cern.ch/lhcb-dpa/project/-/issues/118.