Extract a proto crate out of rpc (#12852)

Release Notes:

- N/A

---------

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

crates/proto/build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let mut build = prost_build::Config::new();
+    build
+        .type_attribute(".", "#[derive(serde::Serialize)]")
+        .compile_protos(&["proto/zed.proto"], &["proto"])
+        .unwrap();
+}