FIFO basic facts

Added a file for some basic lemmas regarding FIFO.

added 3 commits

• d14dc0de - introduce the `preempted_at` job-level predicate
• 9d9ee46f - add a stronger notion of priority policy compliance
• 4cc8d59e - add basic facts about the FIFO scheduling policy

Compare with previous version

added 3 commits

• c65ffcf1 - introduce the job-level predicate `preempted_at`
• 04af1bb4 - add a stronger notion of priority policy compliance
• a0579b47 - add basic facts about the FIFO scheduling policy

Compare with previous version

enabled an automatic merge when the pipeline for a0579b47 succeeds

canceled the automatic merge

enabled an automatic merge when the pipeline for a0579b47 succeeds

merged