Support flow return var for tck connector in studio

Studio component support the flow output var, like "QUERY" info for tMysqlRow:

like the screen shot show, then you can use that var in other component.

And we can define the part in old javajet component xml like this:

<RETURNS>
    <RETURN NAME="QUERY" TYPE="id_String" AVAILABILITY="FLOW"/>
</RETURNS>

AVAILABILITY can be "AFTER" or "FLOW":
1. "AFTER" mean the var is used after current component done, and value is set once, no change. TCK framework support that before already.
2. "FLOW" mean the var is changed on row level, for example, in tfixedflowinput==>tmysqlrow==>tjavaflex case, "QUERY" var is set every input row come, tmysqlrow support the sql like this(ok, find another tck limit ) :

"select * from test where id = '" + row1.id +"'"

then every different input row1 value, different sql for "QUERY", "AFTER" can't work for that.

After current support, you need to set the TCK connector like this:

@Slf4j
@Version(1)
@ReturnVariable(value = "QUERY", availability = FLOW, type = String.class)
@Processor(name = "Row")
@Documentation("JDBC Row component.")
public class JDBCRowProcessor implements Serializable {

And set value in connector code like this (any place, decide by your AVAILABILITY):

@RuntimeContext
private transient RuntimeContextHolder context;

@ElementListener
public void elementListener(@Input final Record record, @Output final OutputEmitter<Record> success,
            @Output("reject") final OutputEmitter<Record>/* OutputEmitter<Reject> */ reject) throws SQLException {
   if (context != null) {
       context.set("QUERY", configuration.getDataSet().getSqlQuery());
   }