Redefine macro checks for reflections

Followup to #16198

Now that the macro instance var no longer exists we can set `has_one?` and `belongs_to?` as false in the AssociationReflection and then set it to true where necessary in the BelongsToReflection or HasOneReflection.

I've also eliminated two locations that were checking against the macro symbol (`macro == :belongs_to`) rather than reusing the existing `belongs_to?` method

I made collection a one liner as well for consistency to follow along with the other methods.