fix(deps): update dependency io.netty:netty-bom to v4.1.121.final (#13760)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Lauri Tulmin <[email protected]>

Author: renovate[bot]

conventions/src/main/kotlin/otel.java-conventions.gradle.kts

@@ -143,7 +143,7 @@ abstract class NettyAlignmentRule : ComponentMetadataRule {
     with(ctx.details) {
       if (id.group == "io.netty" && id.name != "netty") {
         if (id.version.startsWith("4.1.")) {
-          belongsTo("io.netty:netty-bom:4.1.119.Final", false)
+          belongsTo("io.netty:netty-bom:4.1.121.Final", false)
         } else if (id.version.startsWith("4.0.")) {
           belongsTo("io.netty:netty-bom:4.0.56.Final", false)
         }

testing-common/src/main/java/io/opentelemetry/instrumentation/testing/InstrumentationTestRunner.java

@@ -42,6 +42,16 @@
  */
 public abstract class InstrumentationTestRunner {
 
+  static {
+    // In netty-4.1.121.Final unsafe usage is disabled by default on jdk24. This triggers using
+    // a different pooled buffer implementation which apparently breaks when initializing ssl. Here
+    // we switch to unpooled buffers to avoid that bug. We do this here because this code is
+    // executed early for both agent and library tests.
+    if (Double.parseDouble(System.getProperty("java.specification.version")) >= 24) {
+      System.setProperty("io.opentelemetry.testing.internal.io.netty.allocator.type", "unpooled");
+    }
+  }
+
   private final TestInstrumenters testInstrumenters;
 
   protected InstrumentationTestRunner(OpenTelemetry openTelemetry) {