Gen.Set().WithCountLessThan() should trigger "best attempt" set generation

[nth-commit]

This should be a valid generator

Gen.Boolean().SetOf().WithCountLessThan(10)

However, currently it will generate a count between 0 and 10, and if that count is > 2 (max distinct booleans), it will exhaust.

It should be less strict about when constrained by max count, and just do its best.