Enhanced: Use Gson serializer by hard coding in MetatData module

### Environment

* Dubbo version: 2.7.3
* Operating System version: xxx
* Java version: xxx

1. Is it need which the serializer util should be decided by dubbo's user.

Involved method:org.apache.dubbo.metadata.support.AbstractMetadataReport#storeConsumerMetadataTask
line:272
`...

Gson gson = new Gson();
String data = gson.toJson(serviceParameterMap);
doStoreConsumerMetadata(consumerMetadataIdentifier, data);
saveProperties(consumerMetadataIdentifier, data, true, !syncReport);`

Start at org.apache.dubbo.metadata.support.AbstractMetadataReport#storeConsumerMetadataTask and trace how serviceParameterMap is serialized before doStoreConsumerMetadata is called. Determine the required serializer-selection behavior from the issue, then verify that this metadata path no longer relies on an unsuitable hard-coded choice.

Written by the indexing model from the issue text.