Generalization of `.getNanosToWaitForReset()`

Hi, really good library, thanks a lot for your work!

I had to use the 7.0.0-beta-2020-04-18 release only because the ConsumptionProbe has this method. I am using Caffeine as a local cache for buckets and need this information to compute accurate TTLs on buckets every time tokens are consumed. By getting this full refill interval, a bucket can be safely marked as stale after this point in time: we know it will be full, so there is no point keeping it in memory.

Some questions / comments:

1. There isn’t any other way getting this information in the stable release, is there? Using the beta is mandatory?
2. I need to apply the same logic when adding tokens manually but it is a bit absurd: refill what is needed + force refill 1 token + consume 1 token to get the ConsumptionProbe ; It would be useful obtaining this information (.getNantosToWaitForReset()) outside of consumption probes.

[vladimir-bukhtoyarov]

With version 6.4.0 desired behavior can be achieved in the following way:

VerboseResult<Nothing> result = bucket.asVerbose().addTokens(1);
long waitForRefillNanos = result.getDiagnostics().calculateFullRefillingTime();

[helins]

Thanks for your prompt action, works perfectly and does the job 😃