[roll third_party/pigweed] pw_system: Add target_hooks porting layer

Instead of hard-coding against FreeRTOS, uses a porting layer defined in
pw_system/target_hooks.h to enable other schedulers.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/74860

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 55333fa304ae7b8..2c042f9c0098c30
Roller-URL: https://ci.chromium.org/b/8825853488109443217
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8825853488109443217
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7bcbbd179f21234a0d8687d87cd977e40f00d9c8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/76782
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 55333fa..2c042f9 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 55333fa304ae7b8784ef9780d25f713d5068b617
+Subproject commit 2c042f9c0098c30d132f0edf046dfa560bd18186