This replaces uses of `Duration#minusMillis()` and `TemporalUnit`
referencing units of time defined in RSTimeUnits with their definitions.
The Timers plugin constructors are changed to accept implementations of
the `TemporalUnit` interface as they do not require any
`ChronoUnit`-specific APIs. Furthermore, the timer lengths updated use
the game tick lengths described in the OSRS wiki, which generally
closely correspond to the previous length definitions we used.
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