[DEC] Make report download retry count and delay configurable

[drazisil-codecov]

Currently, the delay to retry downloading a report from storage during processing is hard-coded at 20s

https://github.com/codecov/worker/blob/da0d05d286fa8bba53e548b12cc68096796d67a0/tasks/upload_processor.py#L16

And the number of retries, while at a hard-coded default of 5

https://github.com/codecov/worker/blob/da0d05d286fa8bba53e548b12cc68096796d67a0/tasks/upload_processor.py#L15

Is capped at one for the step of fetching report from storage

https://github.com/codecov/worker/blob/da0d05d286fa8bba53e548b12cc68096796d67a0/tasks/upload_processor.py#L67-L68

Given the size of the coverage uploads for our Dedicated Enterprise Cloud customers, it would be good if these values were adjustable on a per instance basis.