Back off on errors other than GRPC 8 (Backpressure)

[jwulf]

Other errors, such as 16 UNAUTHENTICATED, should also cause a backoff. There is no way immediate retries of an unauthed request do anything other than DOS the gateway.

This should be implemented here: https://github.com/camunda/camunda-8-js-sdk/blob/main/src/zeebe/lib/ZBWorkerBase.ts#L511

The question is whether all error conditions should trigger a backoff, or if 16 should just be added to the list.

Intermittent network disruption, or waiting for a gateway to come up are examples where backing off reduces the recovery time of the system, but without protecting a gateway from DOS.

I think in the first instance, I'll add 16 UNAUTHENTICATED to the backoff conditions.