Support a dynamic sleep INTERVAL

[mdkent]

This is the resque-pool side of resque/resque#1920. See the notes there.

[nevans]

I like these PRs. Please see my comments on resque/resque#1920. 🙂

For this PR, we need to ensure backward compatibility. (I'm not sure why CI didn't run the test suite.) We could reflect on method arity (👎🏻) or parameter names (better, but verbose), or we could check for the existence of specific ENV vars (👎🏻 extra coupling), or we could check Resque::VERSION (but that won't work until the next gem version is released). So I guess my vote is checking for parameter names.

I'd prefer if Resque or Resque::Worker had a #work_with_env_defaults method (maybe there's a better name?). Or maybe #work could automatically applied its own ENV defaults? Maybe there's already a method that does that and I'm being lazy by not searching the source code right now? That would reduce this cross-gem duplication. And there were a method in Resque or Resque::Worker that does that, we could use Resque::Worker.respond_to?(:work_with_env_defaults) for backward compatibility. I'd much prefer that over the other approaches.

[mdkent]

Went for the simplest option here in just checking the number of params.

Tested okay here on our staging setup. Tried both the updated resque from resque/resque#1919 and the version from master and both are happy.

[nevans]

@mdkent I've fixed CI on main. Can you go ahead and rebase or merge to include those changes?

Once the matching API in resque/resque#1920 is approved, I think we can go ahead an merge this.

[mdkent]

All set!