[roll third_party/pigweed] pw_rpc: Add the benchmark service

Add the first two RPCs in the pw.rpc.Benchmark service.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/54664

third_party/pigweed Rolled-Commits: 7c658f646853590..31b16ea415615ae
Roller-URL: https://ci.chromium.org/b/8840307158778958640
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8840307158778958640
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ib4d1cde7f5a20bd4fb77f6fbaa5a39d027a5032d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/55222
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 7c658f6..31b16ea 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7c658f646853590869bbed995ca1510ff9608048
+Subproject commit 31b16ea415615ae0c797b4e8e61b5c4732e2b07c