Making the producer backoff algorithm configurable

[JSarvesh]

Describe the solution you would like

Currenty in writer.go, during writebatch function call, we have loop on maxattempts and a backoff delay which is exponential based on attempt and a min and max value as 100ms and 1 sec. Can we have a configurable way where instead of exponential we can have a constant delay between retries before the write fails. attching below snippet of library code

A clear and concise description of what you want to happen.

Supporting documentation

Please provides links to relevant Kafka protocol docs and/or KIPs.