[roll third_party/pigweed] pw_system: Multi-channel configuration

This change adds a configuration to pw_system that supports separate
channels for primary and logging RPC. The immediate motivation is to
support a Fuchsia pw_rpc integration prototype which will have separate
primary and logging clients.

See the docs.rst change for more info.

Original-Bug: b/297076185

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/167158

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 24156dddb964db5..f1192a73c6f201d
Roller-URL: https://ci.chromium.org/b/8771034157827412785
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I550757d433f7b6c4feacc702db2da287bf7612fa
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/169295
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 24156dd..f1192a7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 24156dddb964db57638123c92576a88132893dd8
+Subproject commit f1192a73c6f201d4473b05b09c42a33f38ec343c