Enable Netty Grpc client to reuse the existing Netty allocator

Author: franz1981

extensions/grpc/runtime/src/main/java/io/quarkus/grpc/runtime/supports/Channels.java

@@ -211,6 +211,12 @@ public static Channel createChannel(String name, Set<String> perClientIntercepto
                 // just use the existing Vertx event loop group, if possible
                 Vertx vertx = container.instance(Vertx.class).get();
                 if (vertx != null) {
+                    // see https://github.com/eclipse-vertx/vert.x/pull/5292
+                    boolean reuseNettyAllocators = Boolean.getBoolean("vertx.reuseNettyAllocators");
+                    if (reuseNettyAllocators) {
+                        // let Netty Grpc to re-use the default Netty allocator as well
+                        System.setProperty("io.grpc.netty.useCustomAllocator", "false");
+                    }
                     ncBuilder = ncBuilder.eventLoopGroup(vertx.nettyEventLoopGroup());
                 }
                 builder = ncBuilder