[roll third_party/pigweed] pw_sync: change SpinLock to have a constexpr ctor

Changes the pw::sync::SpinLock facade to have a constexpr
constructor. Outside of making the constructor possible to be
evaluated at compile time, this grossly simplifies the use of the
SpinLock during early boot before static global C++ constructors
are executed.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/36580

third_party/pigweed Rolled-Commits: 8b72a5736ae2761..41b2b3d7dbc2aa8
Roller-URL: https://ci.chromium.org/b/8853128917484615552
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8853128917484615552
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iec2396a6c083502abeb3bf3c187a7447b766d561
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/36801
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 8b72a57..41b2b3d 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 8b72a5736ae276162c40a7530d18f2dbfbd73bd4
+Subproject commit 41b2b3d7dbc2aa812451ca210e927af9311c6277