Don't auto-preload AGAIN during nested renders

[jhollinger]

Fixing an issue with auto and nested renders. When auto was on, nested associations were RE-preloading their subtrees. In many cases this was only a minor issue. But in certain situations (lots of manual preloads + field blocks that were really associations), it was a huge net loss of performance.

This is fixed by stricter matching in the extension. Preloading now only occurs if the rendered object's class is exactly ActiveRecord::Relation or ActiveRecord::AssociationRelation. Subclasses like ActiveRecord::Associations::CollectionProxy will no longer match, ensuring we don't preload on nested associations.

Since this is a significant issue, I've included a version bump so we can release asap. Also enabled appraisal in GH Actions.

[jhollinger]

At @njbbaer's suggestion I attempted to use instance_of? instead of comparing strings. Sadly, this doesn't work as ActiveRecord is doing some magic:

q = Project.all
q.class.name
=> "ActiveRecord::Relation"

q.class
=> "Project::ActiveRecord_Relation"