Made tests for JSONEachRow readers to generate more data and cover more types

Author: chernser

clickhouse-data/src/main/java/com/clickhouse/data/ClickHouseDataType.java

@@ -177,8 +177,7 @@ public static Map<Class<?>, Integer> buildVariantMapping(List<ClickHouseDataType
         return variantMapping;
     }
 
-    public static final Map<ClickHouseDataType, Set<Class<?>>> DATA_TYPE_TO_CLASS =
-            Collections.unmodifiableMap(dataTypeClassMap());
+    public static final Map<ClickHouseDataType, Set<Class<?>>> DATA_TYPE_TO_CLASS = dataTypeClassMap();
     static Map<ClickHouseDataType, Set<Class<?>>> dataTypeClassMap() {
         Map<ClickHouseDataType, Set<Class<?>>> map = new HashMap<>();