Should we advertise min-bid to builders?

Today, min-bid is a global variable configured in [mev-boost](https://github.com/flashbots/mev-boost/blob/c48dbe4dfe97d74a724e701ee69d55c93dbb318e/cli/flags.go#L166).

It might make sense to advertise the min-bid to builders via either registrations, `BuilderPreferences` or [ProposerPreferences](https://github.com/ethereum/consensus-specs/blob/a21e27dd861e770368df3a16e393efe1ec2e0efb/specs/gloas/p2p-interface.md#L88) in the consensus-specs, so that builders can avoid bidding below the min-bid i.e the reserve price and have a potentially inefficient auction for builders and validators.

Start with mev-boost's cli/flags.go min-bid definition, then read the BuilderPreferences and ProposerPreferences references in the issue. Determine whether and where min-bid should be advertised, and consider the required builder-specs or consensus-specs changes; done means the protocol approach and affected specification are agreed and documented.

Written by the indexing model from the issue text.