QoL improvement: MaxReconnectToBroker and BackoffPolicy UX improvements

**Is your feature request related to a problem? Please describe.**
Usability problems:
- MaxReconnectToBroker is a `*uint` for what seems to be no good reason. Pointers to primitive ints are rare and unusual in public APIs.
- BackoffPolicy conceptually controls the same things as MaxReconnectToBroker, having them separate is confusing.

**Describe the solution you'd like**
- Combine MaxReconnectToBroker and BackoffPolicy into a single policy struct that can be supplied.
- Either stop passing max-reconnects as a pointer, or document how/when it should be used as a pointer (i.e. written through).

These would be breaking public API changes, so this may be a WONTFIX on that basis.