[roll third_party/pigweed] pw_transfer: Python & C++ integration test

Basic tests for transmitting data between a Python client and a C++
server using pw_transfer.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/54707

third_party/pigweed Rolled-Commits: e04d4687944e0a1..2253040d12b3133
Roller-URL: https://ci.chromium.org/b/8839802586692050432
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8839802586692050432
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I83f620760ef0992e1edc808213760c2df0f79f8b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/56121
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 e04d468..2253040 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit e04d4687944e0a1e8f9e61c206d644ad7db987f2
+Subproject commit 2253040d12b3133e374d1814673f82d6f09f7565