More usable LB policy in 302 backend

[ZenithalHourlyRate]

Currently an exprimental 302 backend is deployed, you may use https://mirrors.mirrorz.org or its alias https://m.mirrorz.org (unavailable when posting this issue because of DNS) or https://mirrors.zenithal.workers.dev to play with it.

As suggested in README.md of directory /302, the current Newest policy is not optimal for users. Hence this issue is opened for discussion on this topic.

We may do the following things here:

1. Propose new policy and its needed information/metadata
2. Discuss what the Monitor should collect
3. Discuss the metadata that that protocol mirrorz.json should provide
4. Post your experiences/feeling about using https://mirrors.mirrorz.org