SinkRecord adds an overridden method (apache#8038)

Motivation
When I was writing the io connector, I needed to use Message in the sink, but SinkRecord did not implement the getMessage method.

Modifications
Add the implementation of getMessage and getEventTime to SinkRecord.

Verifying this change
No needed.

pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/instance/SinkRecord.java

@@ -25,6 +25,7 @@
 import lombok.Data;
 
 import lombok.extern.slf4j.Slf4j;
+import org.apache.pulsar.client.api.Message;
 import org.apache.pulsar.client.api.Schema;
 import org.apache.pulsar.client.impl.schema.KeyValueSchema;
 import org.apache.pulsar.functions.api.KVRecord;
@@ -106,4 +107,13 @@ public Schema<T> getSchema() {
         return null;
     }
 
+    @Override
+    public Optional<Long> getEventTime() {
+        return sourceRecord.getEventTime();
+    }
+
+    @Override
+    public Optional<Message<T>> getMessage() {
+        return sourceRecord.getMessage();
+    }
 }