[Requires Design] Add `messages` parameter to more `prompt.py` functions, including `gen_prompt` and `gen_examples`

[alat-rights]

[Requires Design] Add `messages` parameter to more `prompt.py` functions, including `gen_prompt` and `gen_examples`

[alat-rights]

gen_prompt now has experimental support for messages, but I'm skeptical of how useful this is.

• If you want to respond to that message thread, you now lose your system prompt, since there's no way to add that to messages which is just a list of MessageParams.

It's also not clear to me how likely this use-case is. In the gen_prompt case, it seems that it'd mostly only be useful if you were in a REPL and trying to have a conversation with the prompt generator.

It seems to me that the more useful feature would be for gen_prompt, gen_examples, etc. to easily give you a singleton list containing a MessageParam with role "user". I could actually see this meaningfully reducing boilerplate, and making it faster to directly run outputs from these functions.