[roll third_party/pigweed] pw_rpc: Prevent starting calls with channel ID 0

- Channel ID 0 (Channel::kUnassignedChannelID) cannot be used for calls,
  and any packets with channel ID 0 are already rejected by RPC
  endpoints. Add a PW_CHECK() that crashes if code attempts to start a
  call on channel 0.
- Add a test for invoking a call on an unknown channel. No test is added
  for starting calls on channel 0, since pw_unit_test does not support
  testing that assertions failed.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/127036

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: d12ae88c1199d8f..00e693c6fb7b942
Roller-URL: https://ci.chromium.org/b/8790411805940775825
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0e1df97c6f49816cc483ae165c08bb8634b25bea
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/127091
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/third_party/pigweed b/third_party/pigweed
index d12ae88..00e693c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit d12ae88c1199d8f94573114080d05e493d4ae171
+Subproject commit 00e693c6fb7b9423fa31475b6abe63bca2fd01d3