Merge branch 'remove-banzai-pre-process' into 'master'

Move pre_process into render_result

This MR moves `Banzai::Renderer.pre_process` into `Banzai::Renderer.render_result`.

The `pre_process` method was called even when its output would be ignored. See 11a5a4f359ee57029dbfcc9185fc6b47243ea2aa for more details.

See merge request !4830