Convert repo into workspace for use as shared reth components library

[0xForerunner]

We'd love a place to put our reth component crates (p2p flashblocks, flashblock payload builder, fBAL builder, fBAL verifier, etc..

I'm open to other solutions, but I think it makes sense to convert this repo into a workspace so it can effectively be used to share these components. These components could then be converted into steps for use internally within the rblib pipeline.

[julio4]

Hey yes this is planned for very soon!
The plan is to separate first in two main crates:

• rblib-core: for the payload/checkpoint api
• rblib-pipeline: for the pipeline framework/sdk

We can then add a step library where we can collect all community contributions.