Specify flag passing to `obolup` (or obol)

[OisinKyne]

Problem to be solved

Obolup as is syncs to main. We should give optionality with regard to what (if any) chain it should sync.

Proposed solution

Make a spec document for the UX of chain management on the stack. Should it be a which network?, a multi-select?, should it be more chain agnostic? etc.

[bussyjd]

Have a k8s flavor by default (kind for now) but specifying the flavor the user can switch

[OisinKyne]

Working on this in #14, but just now realising Helios doesn't yet support Hoodi 🥲 https://github.com/a16z/helios/blob/master/ethereum/src/config/checkpoints.rs#L108

[bussyjd]

Implemented :)