[roll third_party/pigweed] pw_function: Standard callback API

This implements pw::Function, a standard wrapper for callable objects.

This CL is currently provided as a proof-of-concept implementation based
on fbl::Function, and does not necessarily represent the final design of
pw::Function.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/46080

third_party/pigweed Rolled-Commits: f5d7ae3705509bc..99de52de27b9211
Roller-URL: https://ci.chromium.org/b/8844963902523229152
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8844963902523229152
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id052f00947b958d87a258dd94bd67d118f90c29a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/48347
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 f5d7ae3..99de52d 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f5d7ae3705509bc87cb646c5a5c51b515d2bc557
+Subproject commit 99de52de27b921179e3dfba2af3837a9b2a11985