[roll third_party/pigweed] pw_rpc: Support opening a ServerReader/Writer

- Deprecate open() in favor of active(), which isn't ambiguous about
  whether it's a verb or adjective and doesn't conflict with Open().
- Support opening a ServerReader/Writer object server-side, without a
  client calling the RPC. This is helpful for testing and in situations
  when the server needs to send a response to an RPC the client hasn't
  called the RPC yet (e.g. respond to a Reset() RPC after rebooting).

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/57882

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5ebf8add166d5ba..5a3a36bd5c3dcba
Roller-URL: https://ci.chromium.org/b/8836426106156585281
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8836426106156585281
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ide9c2923fd4fc693ec15fc7d086c4c61beba75ac
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/60581
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 5ebf8ad..5a3a36b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5ebf8add166d5ba4eecb4617069e9e531c84c016
+Subproject commit 5a3a36bd5c3dcba83626e0aa7de455870ccc3051