Investigate priority implementation

[trader-payne]

There are two types of priorities I want to have:

1. Tiered nodes within the same subset/group. Basically within the load balanced nodes, I want to have "distance"-like tiers. A concrete example for this would be having two archive nodes + a full node. It uses the archive nodes by default, but falls back to our full node before going all the way down to the fallback nodes. This can be either for some predefined time, or triggered by a condition.
2. Actual priority of a given node, within the same tier. So a concrete example is having base reth and erigon. I want most of the requests to go to the reth client, so I can set the priority accordingly.

The last option I think it's more suitable for the round robin approach, not really viable for latency/chainhead unless we define some good strategy to be used here. Worth investigating.