The comparison between `Relation` and `CollectionProxy` should be consistent.

Example:

    author.posts == Post.where(author_id: author.id)
    # => true
      Post.where(author_id: author.id) == author.posts
    # => true

Fixes #13506
Make the comparison between 'Relation' and 'AssociationRelation'
consistent.
Ensure that the comparison between 'CollectionProxy' and 'AssociationRelation' is consistent.
Merge pull request #14592 from laurocaetano/equality_between_relation_and_collection_proxy

The comparison between `Relation` and `CollectionProxy` should be consistent.

Conflicts:
	activerecord/CHANGELOG.md