Restore grpc library exclusion in javaagent test classpath

PR open-telemetry#18316 removed the test classpath filter that excluded the grpc
library instrumentation jar from testExperimental, testStableSemconv,
and testBothSemconv. The removed comment explicitly warned that the
bundled ContextStorageOverride breaks these tests, and indeed it does:
with the library on the classpath, the gRPC Context (including its
cancellation) propagates through application executors, causing
clientCallAfterServerCompleted to fail with 'CANCELLED: io.grpc.Context
was cancelled without error'. This was the root cause of recent
testLatestDeps3 job failures on main.

Author: trask

instrumentation/grpc-1.6/javaagent/build.gradle.kts

@@ -53,6 +53,12 @@ tasks {
     testClassesDirs = sourceSets.test.get().output.classesDirs
     classpath = sourceSets.test.get().runtimeClasspath
 
+    // exclude our grpc library instrumentation, the ContextStorageOverride contained within it
+    // breaks the tests
+    classpath = classpath.filter {
+      !it.absolutePath.contains("opentelemetry-grpc-1.6")
+    }
+
     systemProperty("metadataConfig", "otel.instrumentation.grpc.experimental-span-attributes=true")
     jvmArgs("-Dotel.instrumentation.grpc.experimental-span-attributes=true")
   }
@@ -61,6 +67,12 @@ tasks {
     testClassesDirs = sourceSets.test.get().output.classesDirs
     classpath = sourceSets.test.get().runtimeClasspath
 
+    // exclude our grpc library instrumentation, the ContextStorageOverride contained within it
+    // breaks the tests
+    classpath = classpath.filter {
+      !it.absolutePath.contains("opentelemetry-grpc-1.6")
+    }
+
     jvmArgs("-Dotel.semconv-stability.opt-in=rpc")
     systemProperty("metadataConfig", "otel.semconv-stability.opt-in=rpc")
   }
@@ -69,6 +81,12 @@ tasks {
     testClassesDirs = sourceSets.test.get().output.classesDirs
     classpath = sourceSets.test.get().runtimeClasspath
 
+    // exclude our grpc library instrumentation, the ContextStorageOverride contained within it
+    // breaks the tests
+    classpath = classpath.filter {
+      !it.absolutePath.contains("opentelemetry-grpc-1.6")
+    }
+
     jvmArgs("-Dotel.semconv-stability.opt-in=rpc/dup")
     systemProperty("metadataConfig", "otel.semconv-stability.opt-in=rpc/dup")
   }