Function runRender

Execute the render subcommand.

Output destination:

• If --out is set, the bytes are written there.
• If --out is omitted and the format is textual (json/dot/svg/html), the text is written to stdout via log.
• If --out is omitted and the format is binary (png/jpeg), a default filename is generated via defaultBinaryOutPath and the bytes are written there. The previous "binary requires --out" error is gone.