Clarify maximum parameter ranges in minorminer.find_embedding

**Current Problem**
Some parameters such as max_no_improvement, inner_rounds, chainlength_patience, timeout take integer values, but it is useful to set them to effectively infinite for sake of benchmarking. I.e we fix the timeout to a finite value and work to that timeout (or fix some other parameter with unbounded timeout). The documentation doesn't currently make it clear how to do this.

**Proposed Solution**
Workarounds are available setting values to -1 or None in some cases, or simply a very large integer that can be assumed safe under any type of casting like 1000000, documentation could simply be improved to make this clear.

**Alternatives Considered**
None

**Additional context**
Add any other context here.