feat: string deserialization for prost enums (#2316)

Use pbjson to support string deserialization for enum fields

This allows TOML configs like:
    chainType = "Inbound"
instead of:
    chainType = 1

- Maintain backward compatibility with integer values
- Default serialization format is now string

easytier/src/proto/tests.rs

@@ -1,4 +1,5 @@
 include!(concat!(env!("OUT_DIR"), "/tests.rs"));
+include!(concat!(env!("OUT_DIR"), "/tests.serde.rs"));
 
 use std::sync::{Arc, Mutex};