[roll pigweed] pw_rpc: Add PacketMeta

PacketMeta allows users of pw_rpc to examine information about a
packet prior to processing it fully with ProcessPacket. This allows
packets targeting different channels or services to be filtered and
processed within different contexts.

A key motivation of this is to enable users to run ProcessPacket for
certain service+channels on a specific thread, a new thread, or a work
queue, rather than processing all requests on a single main RPC thread.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/103960

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: f8f2c9b63667116..1d85cfee0e4d08e
Roller-URL: https://ci.chromium.org/b/8807009111229882737
Cq-Cl-Tag: roller-builder:pigweed-zephyr-roller
Cq-Cl-Tag: roller-bid:8807009111229882737
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I10ee6dbff3a6b4734e1363abfa90dad36de3d44b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/104402
Bot-Commit: 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/pigweed b/pigweed
index f8f2c9b..1d85cfe 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit f8f2c9b636671165c1eda45e81f62db9e46fd229
+Subproject commit 1d85cfee0e4d08e7749eaeadf4e270c93e5e6eaf