[Router] Add bucket-aware policy domains and native cache indexing (#38108)

Signed-off-by: Vincent Gao <vincentbo@linux.alibaba.com>
Co-authored-by: inkcherry <mingzhi.liu@amd.com>
Co-authored-by: yangbodong22011 <13137470+yangbodong22011@users.noreply.github.com>

experimental/sgl-router/sgl-kv-indexer/build.rs

@@ -2,9 +2,14 @@
 // SPDX-License-Identifier: Apache-2.0
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Parent hashes need proto3 presence semantics to distinguish roots from
+    // valid hash values. Use the bundled compiler to keep codegen stable.
+    let mut config = tonic_prost_build::Config::new();
+    config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
+
     tonic_prost_build::configure()
         .build_client(true)
         .build_server(true)
-        .compile_protos(&["proto/kv_indexer.proto"], &["proto"])?;
+        .compile_with_config(config, &["proto/kv_indexer.proto"], &["proto"])?;
     Ok(())
 }