[Issue-2122] [pulsar-client] Adding configuration for backoff strategy (#3848)


Fixes #2122 

### Motivation

Current backoff strategy is set by default and is too aggressive. What we should do is allow it to be configurable by the user.

### Documentation

  - Does this pull request introduce a new feature? (yes)
  - If yes, how is the feature documented? (not sure)
1 file changed