[roll third_party/pigweed] pw_rpc: Run tests with completion callback config enabled

Before this CL, the completion request callback code in pw_rpc was not
exercised in CI. Define a config override to enable running the pw_rpc
tests with that option enabled in CI and add to bazel_test.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/187172

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 51936c939a01ab9..f0732862b312cef
Roller-URL: https://ci.chromium.org/b/8759244935485402625
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia20f396fda61683b7bf30ac5602a3fe21dc0a47b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/187375
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 51936c9..f073286 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 51936c939a01ab97a33929711c4bc1e8e5d40e6e
+Subproject commit f0732862b312cef64c0819d9d2c58a4524372904