[roll third_party/pigweed] pw_rpc: Java client

- Initial commit of the pw_rpc Java client and tests. The API will be
  refactored and simplified, but is functional in its current state.
- Download pw_rpc's Java dependencies with Maven in Bazel.
- Add a BUILD.bazel file that sets up the Java plugin for the AutoValue
  library (https://github.com/google/auto).

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/72700

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 28e1162b719beef..3b4f89a26c4d16f
Roller-URL: https://ci.chromium.org/b/8828378471502612449
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8828378471502612449
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I551799a86291d9c223124a5f3e7a31a66bcfa44c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/72865
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 28e1162..3b4f89a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 28e1162b719beef6930fa93f08ae17b64b5764f1
+Subproject commit 3b4f89a26c4d16f7dd5cb0b13d2a932e8be9dfde