Move pre_process into render_result

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?

No.

Why was this MR needed?

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

What are the relevant issue numbers?

None

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together