[batch] Consider renaming tables and columns for better clarity

[jigold]

What happened?

Consider making the following changes to the names of tables and columns now that job groups are in. This will require a shutdown of Batch during the database migration.

• job_groups_cancelled.id -> job_groups_cancelled.batch_id
• job_groups_n_jobs_in_complete_states.id -> job_groups_n_jobs_in_complete_states.batch_id
• job_group_self_and_ancestors.level -> job_group_self_and_ancestors.distance
• job_group_self_and_ancestors -> ???? (We couldn't come up with a better name for this table, but we should try again)

Version

0.2.128

Relevant log output

No response