Add support for additional remote code execution environments, e.g. Riza

[andrewmbenton]

I'd like to play with this in some projects/demos for Riza (https://riza.io), which can remotely run Python/JS in isolation via an API. I'm happy to make an attempt at adding support myself, though most testing will be manual.

1. What is the motivation behind this feature? Is it related to a problem or frustration with the library? Is it
   a feature related to something you need for a project? Is it something you worked on and think it could benefit
   the community?

   Whatever it is, we'd love to hear about it!

I work on Riza so this is specifically useful to me and my team. But having multiple remote execution options would be generally helpful.

2. Describe your requested feature in as much detail as possible. The more you can tell us about it, the better
   we'll be able to help you.

The feature is just to add a class named RizaExecutor which the CodeAgent could use for remote code execution. See proposed code snippets below.

3. Provide a code snippet that demonstrates the feature's usage.

agent = CodeAgent(..., use_riza_executor=True)
# Or perhaps to make this more flexible
agent = CodeAgent(..., executor=RizaExecutor())

4. If the feature is related to a paper, please include a link.
   N/A

[aymeric-roucher]

I like the executor argument! You could propose a PR with Riza indeed, happy to review this!
One note: if you want to get traction, it's best to propose 0-friction setup, i.e. a turnkey solution without even needing an API key (with rate limit?)