[fix](Nereids) add 'integer' as alias of int type (#15983)

fe/fe-core/src/main/java/org/apache/doris/nereids/types/DataType.java

@@ -197,6 +197,7 @@ public abstract class DataType implements AbstractDataType {
                 return TinyIntType.INSTANCE;
             case "smallint":
                 return SmallIntType.INSTANCE;
+            case "integer":
             case "int":
                 return IntegerType.INSTANCE;
             case "bigint":

regression-test/suites/nereids_syntax_p0/function.groovy

@@ -168,5 +168,10 @@ suite("nereids_function") {
             ) AS level
         from window_funnel_test t;
     """
+
+    test {
+        sql "select cast(1.2 as integer);"
+        result([[1]])
+    }
 }