[third_party/pigweed] Roll 4 commits

781ca39bf1aec12 pw_assert: Introduce :backend, :backend_impl
588f7e3139c425c pw_format: Enhance Rust tests to check for argumen
c48913eb9e0bc8d docs: Fix some incorrect target names
88fe42a81eb8d01 pw_checksum: Add missing #include <array>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 7d55609f2ff182a..781ca39bf1aec12
Roller-URL: https://ci.chromium.org/b/8753459537075711185
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I10affca0fdbf482de3c3fc5cde3545699cf5fbbc
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/196551
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 7d55609..781ca39 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7d55609f2ff182a07f6bbc13910c9ea911b13e8d
+Subproject commit 781ca39bf1aec1261a9953bf49f77fa06e3f1ed6