simplify `conversion_preserves_equivalence` proof

...and many other proofs:

- Simplify proof of conversion_preserves_equivalence
- Simplify proofs in analysis/facts/behavior/service.v
- Simplify proofs in analysis/facts/behavior/deadlines.v
- Simplify proofs in analysis/facts/behavior/arrivals.v
- Fix order of arguments in identical_prefix_inclusion
- Simplify proofs in analysis/facts/behavior/completion.v