TraceProcessor: Add binary RPC interface

Doc: https://docs.google.com/document/d/1Xno5BovxYweoSC6G3UjcsVJD65FLFTUjzUR0FXUmt0s/edit?usp=sharing
This CL doesn't wire it up yet to RPC or Wasm.
Next CLs will do.

Test: perfetto_unittests --gtest_filter=QueryResultSerializerTest.*
Change-Id: I08b7bb638fe4deabf41e14e30fc548aec9ab58e4
Bug: 159142289
diff --git a/BUILD b/BUILD
index fa4dc90..13ad87a 100644
--- a/BUILD
+++ b/BUILD
@@ -815,6 +815,8 @@
 filegroup(
     name = "src_trace_processor_rpc_rpc",
     srcs = [
+        "src/trace_processor/rpc/query_result_serializer.cc",
+        "src/trace_processor/rpc/query_result_serializer.h",
         "src/trace_processor/rpc/rpc.cc",
         "src/trace_processor/rpc/rpc.h",
     ],