Add identities and lists of participants to prompts

[cjqian]

No description provided.

[vivtsai]

Could we have a setting to specify if the participants', e.g., names/pronouns should be included? For instance, I could see one experiment wanting to show the LLM pronouns/names, vs. wanting to only show gender-neutral identifiers.

(If the distinction isn't needed, let's make a note in the "agent/prompting scope" document we plan to put together.