[Fix](Variant) forbit create variant as key #36555 (#36578)

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/info/ColumnDefinition.java

@@ -226,6 +226,9 @@ public class ColumnDefinition {
             } else if (type.isJsonType()) {
                 throw new AnalysisException(
                         "JsonType type should not be used in key column[" + getName() + "].");
+            } else if (type.isVariantType()) {
+                throw new AnalysisException(
+                        "Variant type should not be used in key column[" + getName() + "].");
             } else if (type.isMapType()) {
                 throw new AnalysisException("Map can only be used in the non-key column of"
                         + " the duplicate table at present.");