fix(document): make array getters avoid unintentionally modifying array, defer getters until index access instead

[vkarpov15]

Summary

#13748 points out that accessing user.hobbies actually modifies the hobbies array if there's a getter on elements of the hobbies array. That is a problem. To fix that, I moved the logic for applying getters from SchemaArray.prototype.applyGetters(), which is also called when you access user.hobbies, and into the top-level applyGetters() function, which is only called by toObject() and toJSON().

As a side effect, in order to avoid breaking Schema UUID tests, we instead need to apply getters on index access. So user.hobbies[0] will fire getters on hobbies.0, but not modify hobbies. That's what the changes to types/array/index.js are for.

Still to investigate: it looks like oneUser.get('hobbies.0') double calls getters with this PR. Worth checking before merging.

Also need to think about whether to merge this in 7.5, or wait for 8.0. The types/array/index.js changes seem a bit too heavy for a patch release.

Examples

[AbdelrahmanHafez]

LGTM. 👍