[roll third_party/pigweed] pw_bytes: SignExtend template

Adds the SignExtend template for expanding the nth bit to the left up
to the size of the destination type.

Original-Bug: b/321114167
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/188456

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: ffc60786179e0c2..40a14982a9506ad
Roller-URL: https://ci.chromium.org/b/8758172995871837713
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ifa27ca982cba633ff3364d40a9c9ede5ffd52276
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/188732
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index ffc6078..40a1498 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit ffc60786179e0c2099ffe2a94f18c12b0e93db46
+Subproject commit 40a14982a9506ada7a7d3803460d267c315299ff