Move pre_process into render_result

Merged yorickpeterse-staging requested to merge remove-banzai-pre-process into master

What does this MR do?

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

Are there points in the code the reviewer needs to double check?


Why was this MR needed?

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

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Does this MR meet the acceptance criteria?