[roll third_party/pigweed] pw_rpc: Classes for client & bidirectional streaming

- Implement RawServerReaderWriter and derived classes. Mostly implement
  NanopbServerReaderWriter.
- Fill out MethodTraits for client/bidirectional streaming.
- Update NanopbMethodSerde argument order to match style used elsewhere
  and Google style.
- Rework MethodImplTester to reduce duplication and test new features.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/51526

third_party/pigweed Rolled-Commits: 952f2d5865cb623..59b37f76a47204c
Roller-URL: https://ci.chromium.org/b/8842215920569825808
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8842215920569825808
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id08f4c21ee7f3fdc17191eb6211b598de1a8bb86
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/52540
Reviewed-by: 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 952f2d5..59b37f7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 952f2d5865cb623237d837c2926fef05186b4cee
+Subproject commit 59b37f76a47204c99dbcdd035146e81e0da44ead