barretenberg breaking change process

[ludamad]

The recent motivation here is the change of ZK to being the default mode for proving. We need to have a well-defined process for breaking changes:

• migration notes need to be drafted when the breaking change is merged
• update documentation and examples in newly created bb docs

[ludamad]

There's probably a bigger discussion around releases happening at the same time here. One of the questions involved in this bigger discussion is likely if bb should get its own patch releases separate from aztec packages. Normally however separate bb releases don't make much sense as most changes would affect protocol versioning

[johnathan79717]

https://github.com/AztecProtocol/barretenberg/issues/1591 could introduce some breaking changes, such as defaulting to solidity.