roll: third_party/pigweed pw_thread: Synchronize LazyInitThreadChecker with atomic

Fix race on init for the lazy init thread checker variant by storing
thread id in atomic and using a compare_exchange_strong to ensure its
only initialized once.

Update usage docs to be more clear.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/336160
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 0175d4951ffd30313e4d1200f72053e1bd3a1404

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 78692a073121d3..0175d4951ffd30
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8700292230269885969
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I15dd6671d27a2c06bfa685d09509d97f454907e7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/336652
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 78692a0..0175d49 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 78692a073121d3221ee8782ab2c1bf30cc4f192d
+Subproject commit 0175d4951ffd30313e4d1200f72053e1bd3a1404