mvp relay

[chirag-bgh]

[ralexstokes]

this should be rebased against the latest changes, but I am interested in supporting some kind of extension like this so the relay can actually validate blocks

I think a first step would be defining a trait for validation and installing in the current main branch, along with the ability to segregate builders into "trusted" vs "untrusted"

then we can provide an implementation for BlockValidation that uses the reth RPC ext API