[roll third_party/pigweed] pw_software_update/py: Verify bundles

Adds verify.py to check update bundle contents and exercise typical
verification paths.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/64982

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 134da64ab8b89e5..c870070bc755f7b
Roller-URL: https://ci.chromium.org/b/8828548797712522353
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8828548797712522353
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I6c738efa171faa36b28622ff181b8a7ca9586eb2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/72540
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 134da64..c870070 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 134da64ab8b89e577344441542869b296ef6c647
+Subproject commit c870070bc755f7bd82f9669c50d5c1b3880d2101