roll: third_party/pigweed pw_protobuf: Add decoder fuzz test

Adds a fuzz test which runs the decoder with arbitrary input buffers to
ensure that it does not crash.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/273093
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: c4fca6b2f2212127f4caf59b362bbfff65ba7c36

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: c783ff2da68378..c4fca6b2f22121
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8721184970335242433
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0aac0473a79d3f44b9487347bc57b4a286d85628
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/273117
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index c783ff2..c4fca6b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c783ff2da68378bb59b07c4d6483eb69e8aa2604
+Subproject commit c4fca6b2f2212127f4caf59b362bbfff65ba7c36