Don't make dependants install protoc #3947

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

I'd like to file a PR with delta-rs (delta-io/delta-rs#892) but it won't pass their CI because we require all our downstream dependencies to install protoc. Let's fix that.

Describe the solution you'd like

Have build.rs automatically download and extract the correct protoc distribution for the build platform into OUT_DIR and use that for the prost build.

Describe alternatives you've considered

1. require users to install it manually
2. PR prost to add this functionality
3. stop using prost

Additional context
Add any other context or screenshots about the feature request here.