grpc: reduce client idle pings to avoid ENHANCE_YOUR_CALM (#7885)

* grpc: reduce client idle pings to avoid ENHANCE_YOUR_CALM (too_many_pings)

* test: use context.WithTimeout and pb constants for keepalive

* test(kafka): use separate dial and client contexts in NewDirectBrokerClient

* test(kafka): fix client context usage in NewDirectBrokerClient

other/java/client/src/main/java/seaweedfs/client/FilerGrpcClient.java

@@ -87,7 +87,7 @@ public class FilerGrpcClient {
                 .maxHeaderListSize(16 * 1024 * 1024)
                 .keepAliveTime(KEEP_ALIVE_TIME_SECONDS, TimeUnit.SECONDS)
                 .keepAliveTimeout(KEEP_ALIVE_TIMEOUT_SECONDS, TimeUnit.SECONDS)
-                .keepAliveWithoutCalls(true)
+                .keepAliveWithoutCalls(false)
                 .withOption(io.grpc.netty.shaded.io.netty.channel.ChannelOption.SO_RCVBUF, 16 * 1024 * 1024)
                 .withOption(io.grpc.netty.shaded.io.netty.channel.ChannelOption.SO_SNDBUF, 16 * 1024 * 1024);