chore: update prost (prost-types & prost-build) from 0.11.0 to 0.12.0

[cheshirskycode]

It works only with batch update

[cheshirskycode]

Hmm..

/home/runner/.cargo/bin/rustup target add --toolchain stable mipsel-unknown-linux-gnu
error: component 'rust-std' for target 'mipsel-unknown-linux-gnu' is unavailable for download for channel 'stable'
If you don't need the component, you can remove it with:

    rustup target remove --toolchain stable mipsel-unknown-linux-gnu
Error: The process '/home/runner/.cargo/bin/rustup' failed with exit code 1

[mxinden]

Thank you for looking into this. I am guessing the failure is related to https://github.com/prometheus/client_rust/pull/98/.

Long run I would like to move away from prost towards quick-protobuf. We had good experience with that in https://github.com/libp2p/rust-libp2p/issues/3024.

@cheshirskycode what do you think? Would you be interested in contributing the above move from prost to quick-protobuf?

[cheshirskycode]

@mxinden, yes, it is interesting. I'm in.

[mxinden]

@cheshirskycode any updates here? Anything I can help with?