[Issue 5454][pulsar-client-cpp]Fix cpp client schema version (#5930)

Fixes #5454 


### Motivation

The current CPP client cannot correctly obtain the schema version, resulting in an error in parsing with java client when sending data with schema using python client.

Test code:

```
import pulsar
import json

from pulsar.schema import *

class Test(Record):
    name = String()
    id = Integer()

client = pulsar.Client('pulsar://localhost:6650');
producer = client.create_producer('test-producer-schema', schema=AvroSchema(Test))
producer.send(Test(name='Hello', id=1))
client.close()
```



### Modifications

* Add set schema version in msgmetadata

### Verifying this change

Add check schema version in unit test SchemaTest

pulsar-client-cpp/lib/ProducerImpl.cc

@@ -287,6 +287,9 @@ void ProducerImpl::setMessageMetadata(const Message& msg, const uint64_t& sequen
         msgMetadata.set_compression(CompressionCodecProvider::convertType(conf_.getCompressionType()));
         msgMetadata.set_uncompressed_size(uncompressedSize);
     }
+    if (!this->getSchemaVersion().empty()) {
+        msgMetadata.set_schema_version(this->getSchemaVersion());
+    }
 }
 
 void ProducerImpl::statsCallBackHandler(Result res, const MessageId& msgId, SendCallback callback,

pulsar-client-cpp/tests/SchemaTest.cc

@@ -36,6 +36,9 @@ TEST(SchemaTest, testSchema) {
     ProducerConfiguration producerConf;
     producerConf.setSchema(SchemaInfo(AVRO, "Avro", exampleSchema));
     res = client.createProducer("topic-avro", producerConf, producer);
+
+    // Check schema version
+    ASSERT_FALSE(producer.getSchemaVersion().empty());
     producer.close();
 
     ASSERT_EQ(ResultOk, res);