Active Record already has the ability to guess the foreign key. With
query constraints we can use the information from the owner class and
that foreign key to infer what the query constraints should be for an
association. This change improves the ergonomics of the query
constraints feature by making it so that you only have to define the
query constraints on the top level model and skip defining it on the
association. There are a few caveats to this as of this PR:

- If the query constraints on the parent are greater than 2, Rails can't
derive the association constraints
- If the query constraints on the parent don't include the primary key,
Rails can't derive the association constraints.
- If the association has an explicit `foreign_key` or
`query_constraints` option set, Active Record won't infer the key.
- I have not implemented support for CPK yet as it's more complex and
maybe not possible since we don't know which key to split on and use
for the foreign association.

Prior to this change you would need to do the following to use query
constraints:

```ruby
class Post
  query_constraints :blog_id, :id

  has_many :comments, query_constraints: [:blog_id, :blog_post_id]
end

class Comment
  query_constraints :blog_id, :id

  belongs_to :blog, query_constraints: [:blog_id, :blog_post_id]
end
```

After this change, the associations don't require you to set the query
constraints, Active Record will generate `[:blog_id, :blog_post_id]`
foreign key itself.

```ruby
class Post
  query_constraints :blog_id, :id

  has_many :comments
end

class Comment
  query_constraints :blog_id, :id

  belongs_to :blog
end
```