Auto merge of #2593 - RalfJung:ci, r=RalfJung
Auto merge of #2593 - RalfJung:ci, r=RalfJung

CI improvements

- cache RTIM for the style checks
- disable fail-fast for main checks so that we can see whether the other jobs are green

rust-lang/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri