API module rework

[julienrbrt]

Having a global API module for separately versioned modules isn't correct.
<To elaborate>

Work breakdown

• Split proto folder (refactor(proto): host module proto files within modules #18758)
• Create buf repository for each module
• Create an api module within each module (or define another design)

ref: #12003

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Once this issue is closed, we will be able to backport #18473

[tac0turtle]

before the final step we should get an adr which defines what are the rules around protobuf we are adhering to. We dont follow protobuf rules and the mix of following and not following is causing issues. We should squash this once and for all

[julienrbrt]

Maybe we don't need an api module at all, and solely use buf autogenerated code: https://buf.build/docs/bsr/generated-sdks/go with the https://buf.build/protocolbuffers/go plugin.

[julienrbrt]

Closing this until we have an actual proposal. We can get away long enough by using buf.build generated sdk and setup buf plugin and improve our buf usage altogether (#19503)