v2.1: ci: introduce ci/docker/env.sh (backport of #3774)

[mergify]

Problem

context: https://discord.com/channels/428295358100013066/560503042458517505/1310571536221995068

it's time to update our ci to ubuntu 22

Summary of Changes

• move all docker related env into ci/docker/env.sh
• use a new tag format for our ci docker image.

CI_DOCKER_IMAGE="anzaxyz/ci:${SANITIZED_BASE_IMAGE}_rust-${RUST_VERSION}_${RUST_NIGHTLY_VERSION}_${ci_docker_hash}"`
```<hr>This is an automatic backport of pull request #3774 done by [Mergify](https://mergify.com).