evolution: add widget parameter for random conditional, with which object to use as random about evolution

[tahini]

For exclusive conditional, the randomProbability could be number | [number, number]. In the first case, the number is the probability to get the random widget. In the second, it is a start/end range between 0 and 1. For example if 50% of hh should get q1 and the other 50% q2, q1 would have [0, 0.5] and q2 would have [0.5, 1]. I wouldn't be sure how to handle 0, 0.5 and 1 though... Inclusive or exclusive? If inclusive, 0.5 would get both... Maybe [{value: number, inc: boolean},{value: number, inc: boolean}]?

Anyway, this will require the random values to be kept in a specific path in the responses. This will also be necessary to be able to set the sampling value when in development mode (see https://github.com/chairemobilite/od_mtl_2023/issues/411)

[tahini]

But implementing this will greatly reduce the burden of survey developers in the future for such questions.