investigate/convert to Calcite's SchemaPlus way of reading calcite models instea...

investigate/convert to Calcite's SchemaPlus way of reading calcite models instead of manually handling JSON

https://github.com/apache/incubator-wayang/blob/9d7ecc49ae91f1bb93bded435310e53513bdd28f/wayang-api/wayang-api-sql/src/main/java/org/apache/wayang/api/sql/calcite/utils/ModelParser.java#L34

```java

package org.apache.wayang.api.sql.calcite.utils;

import org.apache.wayang.core.api.Configuration;
import org.json.simple.parser.ParseException;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.Iterator;
import java.util.Objects;

/*
* TODO: investigate/convert to Calcite's SchemaPlus way of reading calcite models instead of manually handling JSON
*/
public class ModelParser {
private final Configuration configuration;
private final JsonNode json;

public ModelParser() throws IOException, ParseException {
final String jsonString = Files
.readString(new File("wayang-api/wayang-api-sql/src/main/resources/model.json").toPath());
final ObjectMapper objectMapper = new ObjectMapper();

this.json = objectMapper.readTree(jsonString);
this.configuration = null;
}

public ModelParser(final Configuration configuration) throws IOException, ParseException {
final String calciteModel = "{\"calcite\":" + configuration.getStringProperty("wayang.calcite.model")
+ ",\"separator\":\";\"}";
final ObjectMapper objectMapper = new ObjectMapper();

this.json = objectMapper.readTree(calciteModel);
this.configuration = configuration;
}

/**

```

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