[roll third_party/pigweed] pw_status: Optionally add [[nodiscard]] to status

- Add a config option to pw_status that enables [[nodiscard]] to
  pw::Status and pw::StatusWithSize. Default to off.
- Add [[nodiscard]] to pw::Result.
- Add Abseil-style IgnoreError() functions to Status, StatusWithSize,
  and Result.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/46603

third_party/pigweed Rolled-Commits: 463700da9c87c1b..86ec8820cbe56f1
Roller-URL: https://ci.chromium.org/b/8846322256452604368
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8846322256452604368
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I82ab4e63c36fef799d7bc6bd2a9836a92b5f029b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/46745
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 463700d..86ec882 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 463700da9c87c1bd81fffee9b2650e8aa8a7a773
+Subproject commit 86ec8820cbe56f14161438715d9ff6e52a62894b