Update rust-extensions project for the next release

[jsturtevant]

PR #81 upgrades TTRPC to use protobuff 3.x to unblock some work. This is a tracking issue so we can update once we get a new release of the https://github.com/containerd/rust-extensions project

          > This is taking much longer than anticipated, things are moving along but slowly. I am finding it difficult to maintain this patch and work on the Windows implementation with the various changes going in for the youki work.

Any thoughts on pinning to a rev vs a realse so we can start bumping the other dependencies and moving forward on protobuf 3?

I'm good with pinning to a rev as long as we have an issue to track the follow up work. What do others think?

Originally posted by @devigned in #81 (comment)