Added validation for extra extensions if present

migtests/tests/pg/multiple-schemas/validate

@@ -2,6 +2,7 @@
 
 import yb
 import common
+import sys
 
 live_migration = 'false'
 def main():
@@ -157,6 +158,12 @@ def migration_completed_checks(tgt):
 			expectedExtensions.remove("timetravel")
 		for extension in expectedExtensions:
 			assert extension in extensions, f"expected extension is not reported: {extension}"
+
+		# Check for extra/unexpected extensions
+    	extra_extensions = set(extensions) - set(expectedExtensions)
+    	if extra_extensions:
+    	    print(f"ERROR: Unexpected extensions found: {extra_extensions}")
+    	    sys.exit(1)  # Exit with error status
 
 def change_expected_values_for_live_migration():
 	del EXPECTED_ROW_COUNT["Mixed_Case_Table_Name_Test"]