Rollup of 6 pull requests
Successful merges:
- #109660 (Document that SystemTime does not count leap seconds)
- #114238 (Fix implementation of `Duration::checked_div`)
- #114512 (std/tests: disable ancillary tests on freebsd since the feature itsel…)
- #114919 (style-guide: Add guidance for defining formatting for specific macros)
- #115278 (tell people what to do when removing an error code)
- #115280 (avoid triple-backtrace due to panic-during-cleanup)
r? `@ghost`
`@rustbot` modify labels: rollup
7e02fd8251