fix(query): shallow clone $or, $and if merging onto empty query filter

[vkarpov15]

Fix #14567

Summary

Currently, when you call TestModel.find({ $and }), Mongoose doesn't clone the $and. Then Query.prototype.and() uses push() to add onto the $and array, which modifies the existing $and array.

We already have some logic in place from #12944 that shallow clones $and, $or if they're set, but that only currently kicks in if there's an existing $and / $or. With this PR, we'll do a shallow clone on $and, $or if they exist on the user's provided query filter.

Examples

[sderrow]

Thanks! Just a couple thoughts.