feat: add rapidproto generator

[kocubinski]

Description

Closes: #14704

This generator is being used here for work on #10993. Sourced from work in cosmos/cosmos-proto#83

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Author Checklist

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I have...

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• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
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• confirmed the correct type prefix in the PR title
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• reviewed state machine logic
• reviewed API design and naming
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• reviewed tests and test coverage
• manually tested (if applicable)

[tac0turtle]

left one question, utACK

[julienrbrt]

lgtm