pw_trace: Add basic RPCs to get trace

Add a basic RPC service to trace which currently provides 3 RPCs:
  - Enable(bool), Turns tracing on or off
  - IsEnabled, Returns if tracing is currently on or off
  - GetTraceData, Streams the encoded trace data.

This CL also adds a python script which uses these RPCs to retrieve
and decode trace data from a connected device.

Change-Id: Iaceb3fa87017939a17512738101af70bf335504a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/31880
Reviewed-by: Paul Mathieu <paulmathieu@google.com>
Commit-Queue: Rob Oliver <rgoliver@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 0c1ebdb..ae068a3 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -201,6 +201,7 @@
       "$dir_pw_trace:trace_example_basic",
       "$dir_pw_trace_tokenized:trace_tokenized_example_basic",
       "$dir_pw_trace_tokenized:trace_tokenized_example_filter",
+      "$dir_pw_trace_tokenized:trace_tokenized_example_rpc",
       "$dir_pw_trace_tokenized:trace_tokenized_example_trigger",
     ]
   }