Add local EL+CL

[Oisín Kyne]

Problem to be solved

If we go to 6 VCs, that's a hell of a lot of requests to be firing at infura, which isn't all that great anyways.

Proposed solution

Add an EL+CL pair of containers that are not geth + lighthouse. Ideally have fast sync enabled on the CL side so it doesn't take long to get started and healthy.

[Abhishek Kumar]

@OisinKyne Just one pair of container for all 6 charon nodes, right?

[Abhishek Kumar]

I'm trying to do a pair of Nethermind + Nimbus. Let's see how it goes