[scene_manager] Allow setting delimiters for CSV output

[Breakthrough]

Allows setting delimiters for both rows and columns for the write_scenes_list function as well as in the config file for the list-scenes command. #423

Outstanding Tasks:

• [ ] Add CLI tests that verify output with goldens
• [ ] Ensure CLI only allows 1-character separators are allowed (see TODO in code)
  • This is a limitation by the Python CSV module so this will only be enforced by the CLI to provide correct error messages to end users