Before this commit, getting the last job instance/execution required to
load all job instances/executions from the database and filter them
on the client side in memory.
This commit introduces new methods that use database queries to get
the last job instance/execution without the need to load all job
instances/executions. This change improves memory consumption as well as
the performance of starting the next instance of a job.
Resolves BATCH-1784
7c1fbede1b