Allow cancel without retry

[thedmdim]

Previously we couldn't cancel task without sending it to retry queue. Despite the fact that handler returned SkipRetry error, it didn't work correctly. Read from <-ctx.Done() in processor.go:246 caused by canelation were and will be always earlier than returned SkipRetry from handler. That's why task always went to retry queue.

With these changes you are able to cancel task so it will be archived instead of going to retry :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.49%. Comparing base (4f00f52) to head (35edb02).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #988      +/-   ##
==========================================
- Coverage   67.13%   66.49%   -0.65%     
==========================================
  Files          29       29              
  Lines        4300     5745    +1445     
==========================================
+ Hits         2887     3820     +933     
- Misses       1135     1643     +508     
- Partials      278      282       +4     

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[kamikazechaser]

The downside of this approach is that every context cancellation will result in the task being cancelled.. There are some cases where you'd want a certain context cancellation to be retry-able. Right now every cancellation will be retried and I believe most users are used to this behaviour by now.

With 1.20, this kind of checking is possible: https://pkg.go.dev/context#WithCancelCause coupled with errors.Is(context.Cause(ctx), ErrMyRetryableCancelledCtx). This will allow a better experience.

I'd like to keep this PR open and have more discussions around it with more people before we agree on the best way to handle this.