Extract a proto crate out of rpc (#12852)

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

.github/workflows/ci.yml

@@ -74,7 +74,7 @@ jobs:
           version: v1.29.0
       - uses: bufbuild/buf-breaking-action@v1
         with:
-          input: "crates/rpc/proto/"
+          input: "crates/proto/proto/"
           against: "https://github.com/${GITHUB_REPOSITORY}.git#branch=${BUF_BASE_BRANCH},subdir=crates/rpc/proto/"
 
   macos_tests: