roll: third_party/pigweed pw_containers: Implement type-erased POD Deque specialization for

FixedDeque

- Add a PodDequeImpl specialization that mirrors GenericDeque methods,
  but operates on type erased byte ptrs
- Add additonal tests verifying FixedDeque operations work on PODs + inheritance behaviour
- Integrate PodDeque implementation into non kExternalStorage version of
  FixedDeque

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/407172
Original-Revision: 8f6a8b179731bc19eca710e7ea054cfd8937266a

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 5f7d5f061cee08..8f6a8b179731bc
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8676883847870395553
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I148dae8722e66bbfe1faccde78237d854db4581f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/433652
diff --git a/third_party/pigweed b/third_party/pigweed
index 5f7d5f0..8f6a8b1 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5f7d5f061cee08e55e95df81b51203b1611fa458
+Subproject commit 8f6a8b179731bc19eca710e7ea054cfd8937266a