[yugabyte#27554] Ysql: Call YBCFreeStatus in yb_cancel_transaction to fix possible memory leak

Summary:
Seen in

PgCancelTxnTest_Simple.log but possibly contributing to other asan failures too.

`yb_cancel_transaction` does not free the YbcStatus created in
https://phorge.dev.yugabyte.com/diffusion/YBDB/browse/master/src/postgres/src/backend/utils/misc/pg_yb_utils.c$5318

YBCFreeStatus(status); should be called to reclaim memory.

The issue is more visible after 0020131, but is not caused by this diff.

More like a day-0 issue going back to D26550 / 29f8ac4
Jira: DB-17117

Test Plan: yb_build.sh asan --cxx-test pgwrapper_pg_txn_status-test --gtest_filter PgCancelTxnTest.Simple --clang19

Reviewers: jason, pjain, hsunder, telgersma

Reviewed By: hsunder, telgersma

Subscribers: telgersma, ybase, yql

Differential Revision: https://phorge.dev.yugabyte.com/D44636

Author: amitanandaiyer

src/postgres/src/backend/utils/misc/pg_yb_utils.c

@@ -5328,8 +5328,10 @@ yb_cancel_transaction(PG_FUNCTION_ARGS)
 		ereport(NOTICE,
 				(errmsg("failed to cancel transaction"),
 				 errdetail("%s", YBCMessageAsCString(status))));
+		YBCFreeStatus(status);
 		PG_RETURN_BOOL(false);
 	}
+	YBCFreeStatus(status);
 	PG_RETURN_BOOL(true);
 }