[Feature] Add process-local in-memory KV indexer and Router integration (#33370)

Co-authored-by: Wu, Yutong <yutong.wu@amd.com>
Co-authored-by: TianDi101 <ditian12@amd.com>
Co-authored-by: Zhangheng <hzh0425@apache.org>

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

@@ -0,0 +1,10 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 The SGLang Authors
+// SPDX-License-Identifier: Apache-2.0
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tonic_prost_build::configure()
+        .build_client(true)
+        .build_server(true)
+        .compile_protos(&["proto/kv_indexer.proto"], &["proto"])?;
+    Ok(())
+}