Athens: Remove olympus code

[arschles]

Is your feature request related to a problem? Please describe.

As of #772 we're focusing on a global proxy and not on a registry. the code in cmd/proxy is the former and cmd/olympus is the latter.

Describe the solution you'd like

I'd like us to remove the code in cmd/olympus and other related things that only the cmd/olympus code relied on.

Describe alternatives you've considered

None

Additional context

Ref #612

[steakunderscore]

I can take this on as a first PR :)

[michalpristas]

@steakunderscore feel free to split it into multiple PRs if it makes it easier