Finish migration of protobuf generation code from rust-protobuf to prost

[christophermaier]

While #5126 and #5179 moved the Supervisor and Butterfly (respectively) over to the prost crate for Protobuf generation, the Launcher and Eventsrv continue to use the old protobuf crate.

In order to reduce unnecessary dependencies and consolidate code, we should finish migrating everything over to prost. (There will also be less work if we remove eventsrv first.)

In the course of doing this, we should also consider some additional clean-ups. In particular, the code that generates the protobuf code is far more complex and intimidating than it needs to be. Additionally, we have discussed further simplifying that code by not checking in generated code, instead having it be generated on-demand at compile time. This also seems to be standard prost practice.

[baumanj]

Resolved by #6105 and #6153