roll: third_party/pigweed pw_rpc: Add SendPacket API

Allows bypassing packet encoding by allowing a channel output to
implement a SendPacket API that takes the unencoded packet directly.

Hook this up for pw_grpc to skip an extra packet encode.

Original-Bug: 319162657
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/410454
Original-Revision: 930ea070e1d49dda49a0ecd4e40e12fdd61abe27

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 2b2653c5e4858e..930ea070e1d49d
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8678738101032887761
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1808a4e739e2cd1377a086809bd8c233a35f06a6
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/424412

third_party/pigweed

diff --git a/third_party/pigweed b/third_party/pigweed
index 2b2653c..930ea07 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 2b2653c5e4858efe96bd72e399d2adeec6da89eb
+Subproject commit 930ea070e1d49dda49a0ecd4e40e12fdd61abe27