[roll third_party/pigweed] pw_protobuf: Use pw::InlineString for string fields

- Use pw::InlineString instead of pw::Vector<char> for string fields.
- Temporarily overload pw::string::Copy() for pw::InlineString<> to
  simplify transitioning away from pw::Vector<char>.

Original-Requires: pigweed-internal:31961
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/110111

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9f03fc0248c38fa..ef043925474b59d
Roller-URL: https://ci.chromium.org/b/8802569205509902401
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I237e096704eed6981fd7a822c29dbc24c1eb791a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/110952
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 9f03fc0..ef04392 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9f03fc0248c38fa0c11dedddf53f892db9c8eea2
+Subproject commit ef043925474b59d1a134bd3bd10a83a706776eaa