[roll third_party/pigweed] pw_rpc: ChannelOutput buffer handling fixes

- Ensure ChannelOutput buffers are always released when a call is
  * Release any held buffer when aborting a server call due to an error.
  * Permit calling AcquirePayloadBuffer() on an inactive call, but
    return an empty buffer if it is called while inactive. Previously,
    this was disallowed, but it may not be possible to prevent an
    accidental AcquirePayloadBuffer() on a closed call if it is closed
    by a different thread.
  * Release any held buffer when a client call goes out of scope or is
- Extend locking annotations to cover setting callbacks.
- Expose the function to end client streams as CloseClientStream().

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/78622

third_party/pigweed Rolled-Commits: 36a1ef7322c44fc..0c87be526cb2bbc
Roller-URL: https://ci.chromium.org/b/8825014814722522689
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8825014814722522689
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9b0871827003d93d955ec244b4a6eecfc7c84e13
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/78591
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 36a1ef7..0c87be5 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 36a1ef7322c44fc5a9566783674a435a49897abf
+Subproject commit 0c87be526cb2bbc0ef32896f6548e14c047f4733