types(document): add generic param to depopulate() to allow updating properties

[vkarpov15]

Fix #14876

Summary

Right now doc.depopulate() just returns this, which may be incorrect if paths are depopulated. This PR adds generic parameter, similar to how doc.populate<{ user: UserType }>('user') returns document with user property updated, doc.depopulate<{ user: ObjectId }>('user') also updates the user property type.

Examples

[hasezoey]

LGTM, if i see this correctly, it will now merge the types instead of overwriting? example, instead of PopulatedType changing to ObjectId it is now PopulatedType | ObjectId?

[vkarpov15]

No, MergeType explicitly overwrites property type. So user property will be of type ObjectId, overwriting the populated type

[hasezoey]

nevermind, didnt see that in the last expectType's they were different objects, though they were the same (populatedCar, depopulatedCar)