chen - alphabetical order of o_f return

Signed-off-by: Jialiang Liang <jiallian@amazon.com>

Author: RyanL1997

core/src/main/java/org/opensearch/sql/expression/function/udf/RexOffsetFunction.java

@@ -84,7 +84,7 @@ public static String calculateOffsets(String text, String patternStr) {
         groupIndex++;
       }
 
-      java.util.Collections.reverse(offsetPairs);
+      java.util.Collections.sort(offsetPairs);
       return offsetPairs.isEmpty() ? null : String.join("&", offsetPairs);
     } catch (PatternSyntaxException e) {
       throw new IllegalArgumentException(

core/src/test/java/org/opensearch/sql/expression/function/udf/RexOffsetFunctionTest.java

@@ -28,7 +28,7 @@ public void testCalculateOffsetsWithMultipleNamedGroups() {
     String text = "SMITH";
     String pattern = "(?<first>[A-Z])(?<rest>[A-Z]+)";
     String result = RexOffsetFunction.calculateOffsets(text, pattern);
-    assertEquals("rest=1-4&first=0-0", result);
+    assertEquals("first=0-0&rest=1-4", result);
   }
 
   @Test
@@ -70,7 +70,7 @@ public void testCalculateOffsetsWithComplexPattern() {
     String text = "ABC123DEF";
     String pattern = "(?<letters>[A-Z]+)(?<numbers>[0-9]+)(?<moreletters>[A-Z]+)";
     String result = RexOffsetFunction.calculateOffsets(text, pattern);
-    assertEquals("moreletters=6-8&numbers=3-5&letters=0-2", result);
+    assertEquals("letters=0-2&moreletters=6-8&numbers=3-5", result);
   }
 
   @Test