Add rust-protobuf support to benchmarking

[GuyLewin]

Added support for benchmarking https://github.com/stepancheg/rust-protobuf

[GuyLewin]

This error seems to be related to Bitcode, I don't think this was caused due to my changes.

[djkoloski]

I'll take a look at this after work. It looks like bitcode released a new version recently, so maybe something went wrong here.

[GuyLewin]

Yeah @djkoloski fix is just to upgrade pinned version. Seems like bitcode_derive dependency was too new and became incompatible with our pinned version.
Here's a PR: #102

[GuyLewin]

@djkoloski i need to match my protoc version to the one in CI, will push a fix

[djkoloski]

Thanks for the PR! CI should finish in an hour or two.

[mumbleskates]

we can bump up the version of the ci protoc too if that should be affecting more than it used to be now. previously it was only used by prost to preprocess message definitions into descriptor protos. it probably makes sense to keep it within a few releases of latest