Style tweaks to rwlocks.

- Remove unneeded imports
- Remove double spaces and insert space before colons
- Shorten long lines
- Favor `(.. & .. & ..)` over nesting `[.. [.. ..]]`
- Use `injection` intro patterns
- Favor `%H` over `"%H"`
- Use `first by eauto` instead of `first eauto` since the latter does not fail if `eauto` fails