pw_rpc: Python client & C++ server integration test

- Create utilties for interacting with a host binary running a pw_rpc
  server using HDLC over a socket.
- Write a test that runs commands in a Python client on a C++ server.

Change-Id: I1da75c9d4e989112b392c77c82bdab82a2ea60d3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/54665
Reviewed-by: Alexei Frolov <frolv@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>
diff --git a/pw_rpc/BUILD.gn b/pw_rpc/BUILD.gn
index 6cc8dbc..f83d498 100644
--- a/pw_rpc/BUILD.gn
+++ b/pw_rpc/BUILD.gn
@@ -158,6 +158,16 @@
   visibility = [ "./*" ]
 }
 
+pw_executable("test_rpc_server") {
+  sources = [ "test_rpc_server.cc" ]
+  deps = [
+    ":benchmark",
+    "system_server",
+    "system_server:socket",
+    dir_pw_log,
+  ]
+}
+
 config("private_includes") {
   include_dirs = [ "." ]
   visibility = [ ":*" ]