[roll third_party/pigweed] pw_protobuf: Fix names that collide with internals

Protobuf-to-C++ code generation creates nested types named `Message` and
`Fields` inside of structs generated from protobuf messages, so we need
to fix proto identifiers that conflict with them. We could do this only
in nested contexts, but this change applies the change consistently to
keep both the implementation and the spec relatively simple.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97745

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: b030b954fa0c6b0..be1b751a77e9af1
Roller-URL: https://ci.chromium.org/b/8810714851063225745
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8810714851063225745
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9ef3353ab5c586402c217531029275cbc8dbaa65
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/99240
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 b030b95..be1b751 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b030b954fa0c6b013ca066e48c0e6269112bb8c6
+Subproject commit be1b751a77e9af16e02025649ad1a703258d244f