[roll third_party/pigweed] pw_cli: Script for generating 'Requires:' CLs

Add script for generating transitive 'Requires:' CLs to unnamed internal
Gerrit instances. For now putting into pw_cli because this doesn't seem
to need its own module and there's nowhere better to put it.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/28280

third_party/pigweed Rolled-Commits: b4935f041a99623..ff592cec8a5e994
CQ-Do-Not-Cancel-Tryjobs: true
Roller-URL: https://ci.chromium.org/b/8858204664117887712
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8858204664117887712
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia03e5ba84aecb76cccbeacbf42fca36db86c4e08
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/29461
Reviewed-by: 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 b4935f0..ff592ce 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b4935f041a9962356d97ed7cd93c177b5953890a
+Subproject commit ff592cec8a5e99410985d699d14b799ef4a784c4