Stricter launchd -> StartCalendarInterval type:
- Verify that the integers passed to `Minute`, `Hour`, etc. are within
range.
- When provided, the value for StartCalendarInterval must be a non-empty
list of calendar intervals and must not contain duplicates entries
(throw an error otherwise).
- For increased flexibility and backwards-compatibility, allow an
attrset to be passed as well (which will be type-checked and is
functionally equivalent to passing a singleton list). Allowing an
attrset or list is precisely in-line with what `launchd.plist(5)`
accepts for StartCalendarInterval.
Migrate `nix.gc.interval` and `nix.optimise.interval` over to use this
new type, and update their defaults to run weekly instead of daily.
Create `modules/launchd/types.nix` file for easier/modular use of
launchd types needed in multiple files.
Documentation:
- Update and improve wording/documentation of launchd's
`StartCalendarInterval`.
- Improve wording/documentation of `nix.gc.interval` and
`nix.optimise.interval` ("time interval" can be misleading as it's
actually a "calendar interval"; e.g. `{ Hour = 3; Minute = 15;}`
runs daily, not every 3.25 hours).
