testing: added junit rule for in-process servers

GrpcServerRule configures an in-process server and channel. It is
useful for asserting requests being made to a service. A consumer can
create a mock implementation of their service that records each
request, then make assertions on those records in their test.
diff --git a/settings.gradle b/settings.gradle
index d9ea440..ba0e640 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -10,6 +10,7 @@
 include ":grpc-netty"
 include ":grpc-grpclb"
 include ":grpc-testing"
+include ":grpc-testing-proto"
 include ":grpc-interop-testing"
 include ":grpc-all"
 include ":grpc-benchmarks"
@@ -27,6 +28,7 @@
 project(':grpc-netty').projectDir = "$rootDir/netty" as File
 project(':grpc-grpclb').projectDir = "$rootDir/grpclb" as File
 project(':grpc-testing').projectDir = "$rootDir/testing" as File
+project(':grpc-testing-proto').projectDir = "$rootDir/testing-proto" as File
 project(':grpc-interop-testing').projectDir = "$rootDir/interop-testing" as File
 project(':grpc-all').projectDir = "$rootDir/all" as File
 project(':grpc-benchmarks').projectDir = "$rootDir/benchmarks" as File