Migrate to malaquite once reaching beta or release

[raulk]

Informal Systems have released a Rust version of CometBFT: https://github.com/informalsystems/malachite It's in pre-alpha stage, so still a long way to go for a potential migration, but we should keep tabs on it. If it can operate embedded as a library, we could get rid of significant complexity in the codebase caused by the need to run multiple processes (CometBFT and Fendermint). Concretely:

• Infra scripts complexity.
• Materializer requiring docker images.
• etc.