Move collectors to different package (v2)

[bwplotka]

Reason:

• Concise and focused package, clear boundaries and ability to extend options (currently there is no way to add more options to collector WITHOUT creating more deprecated code).

We can't do it in v1, because we would need to break compatibility. Something for v2.

Attempt: https://github.com/prometheus/client_golang/tree/movegocollector

[stale]

Hello 👋 Looks like there was no activity on this issue for the last 3 months. Do you mind updating us on the status? Is this still reproducible or needed? If yes, just comment on this PR or push a commit. Thanks! 🤗
If there will be no activity in the next 4 weeks, this issue will be closed (we can always reopen an issue if we need!).

[stale]

Closing for now as promised, let us know if you need this to be reopened! 🤗