More toObject() perf improvements

[vkarpov15]

Summary

#14606 caused some performance regression because options is 3rd param to get(), not 2nd.

Also did some work to remove cloneOptions in favor of just plain old options, and relying more on _calledWithOptions to handle the distinction between options that the user specified in the toObject() / toJSON() function call vs options that are set from the schema or mongoose global

Examples

[andrews05]

#14606 caused some performance regression because options is 3rd param to get(), not 2nd.

In my defence... "It was like that when I got here!" 😄

[hasezoey]

LGTM, one question though

[vkarpov15]

@andrews05 no need to apologize, it's our fault, we should've caught that in code review.