[roll third_party/pigweed] pw_rpc: Log Nanopb errors when encode/decode fails

When enabled, Nanopb provides helpful error strings when encoding or
decoding fails. Log the error strings if they're available.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/57780

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b8ca618f12d19b0..9e8ca38f729ad95
Roller-URL: https://ci.chromium.org/b/8838345616935257793
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8838345616935257793
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I70836549aca8dc31c949f4aebf26c49a66aefd17
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/57860
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 b8ca618..9e8ca38 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b8ca618f12d19b01c03c06168d2883f7e0a5c34f
+Subproject commit 9e8ca38f729ad9507290ce0ef91ca040ce7aea60