[FEAT] - Drop unused consensus protocols and code

A [discussion on the recent Tachys CIP](https://github.com/cardano-foundation/CIPs/pull/1149/changes#r2811955948) reminded me of my recent question in one of the consensus working groups:

> Why is there still block production code for old block formats / eras?

See this issue as a discussion (the github discussions seem to be stale on this repo) on what parts of `ouroboros-consensus` are actually unused by the Cardano mainnet and hence could be dropped?

So far I heard:
- Block production of `Byron` blocks
- Ouroboros BFT was never used on mainnet