Adapt to single indent semantics in style guide

[krlmlr]

https://style.tidyverse.org/functions.html#multi-line-function-definitions

It's merely a start, doesn't capture all edge cases yet.

Doesn't conflict with #1137 except for the currently last commit that would be easy to do later on.

CC @MichaelChirico.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 8b9a4a0 is merged into main:

• ✔️cache_applying: 166ms -> 168ms [-2.56%, +5.29%]
• ✔️cache_recording: 521ms -> 520ms [-0.83%, +0.42%]
• ✔️without_cache: 998ms -> 996ms [-1.16%, +0.57%]

Further explanation regarding interpretation and methodology can be found in the documentation.