WIP: refactor builder / rustwide integration

[syphar]

TODO:

• manually test build-server build (see if json, docs, build logs, are all uploaded)
• manually test build-cli build
• clean up log output (tracing fields) generally around the build
• in case of build errors in the doc-builds, I want to see them
• clean up docs_rs_rustwide , check test coverage
• clean up rustwide_builder, check test coverage
• builder cli, print stats in the end, related to limits (so, per build (target / json / cov / html) we show mem, time)

[rustbot]

☔ The latest upstream changes (possibly #3513) made this pull request unmergeable. Please resolve the merge conflicts.