KAFKA-12338: Remove useless MetadataParser

clients/src/main/java/org/apache/kafka/common/protocol/ByteBufferAccessor.java

@@ -133,6 +133,11 @@ public long readVarlong() {
         return ByteUtils.readVarlong(buf);
     }
 
+    @Override
+    public int remaining() {
+        return buf.remaining();
+    }
+
     public void flip() {
         buf.flip();
     }

clients/src/main/java/org/apache/kafka/common/protocol/DataInputStreamReadable.java

@@ -118,6 +118,15 @@ public long readVarlong() {
         }
     }
 
+    @Override
+    public int remaining() {
+        try {
+            return input.available();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     @Override
     public void close() {
         try {

clients/src/main/java/org/apache/kafka/common/protocol/Readable.java

@@ -37,6 +37,7 @@ public interface Readable {
     ByteBuffer readByteBuffer(int length);
     int readVarint();
     long readVarlong();
+    int remaining();
 
     default String readString(int length) {
         byte[] arr = new byte[length];