Side-by-side multimodal arena

[BabyChouSr]

Why are these changes needed?

Side-by-side multimodal chatbot arena. Please comment any advice in terms of the UI or logic! This branch is a fork of the direct chat server and both will be merged together later.

We should add 1. remote storage fix for images #3172 2. push Weilin's code update in order to merge the Claude-3 API provider implementation in #3194 before merging this PR

TODO:

• [x] Add GPT-4-V API
• [x] Make the UI look better
• [x] Remove images in logging? base64 images are big
• [ ] Refactor sampling weights, get battle pair using json? <- we could move this sampling logic to json and then feed it into load_side_by_side_anony to initialize the global variables.

Related issue number (if applicable)

Checks

• [ ] I've run format.sh to lint the changes in this PR.
• [ ] I've included any doc changes needed.
• [ ] I've made sure the relevant tests are passing (if applicable).