[ENHANCEMENT]: adaptively alter speed benchmark

[jessevz]

Description

We notice that certain tasks will consistently give a wrong speed benchmark, making the chunks way to short when speed benchmark is used. It would be great if the speed benchmark can be adapted when the finished chunk time has deviated a lot from the configured chunk time in the task. a solution could be when a chunk has completed and a big deviation is detected, the speed benchmark value in the assignment is adjusted. Another solution could be to alter the chunk time in the task, but this feels a bit hacky

[s3inlc]

Can you more specifically give examples where it is off (type of tasks etc.)?
There is an ongoing problem in hashcat, that certain benchmark results (especially with salted hashes) are quite off: hashcat/hashcat#4637

Also, there is a quite old PR open which tried to address such cases: #729
The reason this one was never merged is that it would also shrink chunks which is not desired due to risk of problems.