Previously Action View was hooking in to _normalize_options to add
:layout, :partial, and :prefix keys to the render options. These were
added whether or not we were rendering a view template.

This commit avoids adding those keys unless we are rendering a template.

This improves performance both by avoiding calculating the templates to
put into this options hash as well as enabling a fast path in `render
json:`, which can only be used when `.to_json` is given no options.