[roll third_party/pigweed] pw_rpc: Make C++ integration test code shareable

- Move C++ client integration test setup code to an integration testing
  library.
- Update pw_rpc/testing.py to use the same arguments for both binaries.
- Support generating a temp directory for integration tests.
- Always create the integration_tests group, but only add it to the
  default target if pw_RUN_INTEGRATION_TESTS is set.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/69380

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 44a911c794fdedd..1215a9dfa8201af
Roller-URL: https://ci.chromium.org/b/8828394766857976097
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8828394766857976097
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ida54cc1108879a0cd4e57a5e2add2b77a5bd9329
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/72800
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 44a911c..1215a9d 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 44a911c794fdedd4f3f37b447cda80e4e5343999
+Subproject commit 1215a9dfa8201af348c072a31437e02f47ebcd05