[roll third_party/pigweed] pw_software_update: Create unsigned update bundles

Testing: Includes baseline unit test coverage
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60043

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: adacd1a992637b1..f345faa70680dfc
Roller-URL: https://ci.chromium.org/b/8836159653391649777
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8836159653391649777
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I54f48e1055ea7ab8fc252e79bae2016f23eb4378
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/60694
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 adacd1a..f345faa 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit adacd1a992637b123c55500f0a88e83325a2876e
+Subproject commit f345faa70680dfc77a9f290c86f646b240a4c01a