Change SpyTime Receiver Function Name from Sleep to SetDurationSlept

[elmq0022]

Reason for Change

Using Sleep for the name incorrectly implies that this function exists to satisfy the Sleeper interface. In fact, the receiver function can use any valid function name. The only requirement is the function's signature matches that of ConfigurableSleeper's sleep member, i.e func(time.Duration).

Why SetDurationSlept

SetDurationSlept accurately describes what the function does. That is SpyTime.SetDurationSlept(5*t.Seconds) sets SpyTime's durationSlept member to 5 seconds.

I will open a PR if the maintainer(s) is(are) interested.