api: new export format

[DifferentialOrange]

This PR introduces new exhaustive export format on collect. It contains structured info on collectors which may be used on export and aggregation build. (Current metrics.collect() result is not enough on Prometheus export. metrics.collect{extended_format = true} is enough.) After this PR, export plugins will be based on extended format info.

See commit messages for more detailed info.

I didn't forget about

• [x] Tests
• [x] Changelog
• [x] Documentation (README and rst)
• [x] Rockspec and rpm spec

Part of tarantool/tarantool#7725 Part of tarantool/tarantool#7728

[github-actions[bot]]

This pull request is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 30 days

[DifferentialOrange]

Closed in favor of https://github.com/tarantool/roadmap-internal/issues/217