tooling: generate protoset file (#17364)

Extends the `proto` make target to generate a protoset file for use with
grpcurl etc.

build-support/scripts/protobuf.sh

@@ -72,6 +72,10 @@ function main {
 
     status "Generated gRPC rate limit mapping file"
 
+    generate_protoset_file
+
+    status "Generated protoset file"
+
     return 0
 }
 
@@ -152,5 +156,11 @@ function generate_rate_limit_mappings {
     }
 }
 
+function generate_protoset_file {
+  local pkg_dir="${SOURCE_DIR}/pkg"
+  mkdir -p "$pkg_dir"
+  print_run buf build -o "${pkg_dir}/consul.protoset"
+}
+
 main "$@"
 exit $?