Deterministic args file stamp

[gontard]

Since #188 the scalafix is almost machine-independent but we discovered that the args was not determinist across machines.
This PR fixes this issue by sorting the classpath and the dependencies before hashing them.

[bjaglin]

I can't find an easy way to guard this against regression via a scripted. The best I could think of would be to compare the args stamp generated by a scripted across JVMs/OS on GitHub Actions using a shared volume somehow, but that's far from trivial... I think this is something we'll have to consider if/when we leverage/advertise support for sbt/sbt#6298 in sbt-scalafix. Until then, the "machine-independant" nature of the sbt-scakafix cache remains partial and best-effort anyway.