[roll third_party/pigweed] pw_rpc_transport: Unblock sockets when stopping

When stopping the transport, close the sockets. Change blocking socket
operations to block in poll and use a separate pipe to unblock poll when
closing the socket.

Also, when closing sockets, disconnect the underlying sockets by using
the socket shutdown API.

Original-Bug: 309680612
Test: Verified socket unit tests pass.
Test: Verified sample-project-default-build-windows and
 pigweed-mac-x86-bazel-test-host-clang succeed.
Test: See details in testing done comment in the code review.
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/181308

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5d6c8774460f969..4f55cd893c39b21
Roller-URL: https://ci.chromium.org/b/8763695274112009089
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia3c8cfc2e22a08ceb2e8a80ee6c7c6635ad4788f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/182395
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 5d6c877..4f55cd8 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5d6c8774460f969b01ba075fb1729aa9eae15933
+Subproject commit 4f55cd893c39b218b8ad116143898b0d9210a964