[third_party/pigweed] Roll 3 commits

b7d686c7f47afe1 pw_presubmit: Show diffs when parser tests fail
559d3789342d9ff pw_format: Add core::fmt macro helper
f2d2129612c13a9 pw_bluetooth_sapphire: Add testonly to testing tar

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 2a06e1549e6d7ea..b7d686c7f47afe1
Roller-URL: https://ci.chromium.org/b/8763055086206674545
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0782daed08f46311e12db5a0a4611397421cbb9a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/183040
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 2a06e15..b7d686c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 2a06e1549e6d7ea2764157a7f65acd24a45358d4
+Subproject commit b7d686c7f47afe1f1f88b3dc82c6a4f8441fb3c7