[🧹 CHORE, API]: Use `oneof` for the option protobuf message

[rustatian]

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What should be improved or cleaned up?

Currently we have a bloated Options message with different fields related to different, unrelated drivers. This doesn't matter from a speed perspective (unused fields don't cost anything), but it does matter from a proto-message architecture perspective. Replace the contents of the options message with `one of' for the different drivers (AMQP, Kafka, etc).