Precise unit for sleep duration and wake time

[szpak]

Prior to, it was required to dig a few levels into to realize they are in millis.

I'm not satisfied with the new names of the field, but I wanted to express that nackSleep is a duration and nackWake is a point of time (the same as currentTimeMillis()). Nevertheless, as they are used internally, it might be sufficient to just change sleep to sleepMillis in the method argument (+ change the javadoc).

java.time.Duriation in the Acknowledgment class would be probably better, however, it is a non-backward compatible change.

[garyrussell]

Given that the nack methods are default methods; I would not object to adding new overloaded methods taking a duration and deprecate the current ones.

[szpak]

Given that the nack methods are default methods; I would not object to adding new overloaded methods taking a duration and deprecate the current ones.

Great. However, as it's a slightly more complicated change, I propose to merge this one as is (with just the "millis" only) and I will create a new one with Duration later on to keep it separate.

[garyrussell]

Thanks; agreed; in future, please just add more commits rather than squashing and force-pushing; it's easier to see what changed (not really a problem for small PRs like this, but important for larger ones). We will squash during the merge.

[garyrussell]

Thanks; cherry-picked to 2.9.x, 2.8.x.