[#23788] YSQL, QueryDiagnostics: Fix testPgssResetBetweenDiagnostics in pg15

Summary:
PostgreSQL 15 introduces a new function, pg_stat_statements_reset_1_7, to handle the pg_stat_statements_reset functionality. As a result, the current changes replicate the existing logic into this new function to maintain compatibility with the updated system.
Jira: DB-12692

Test Plan: ./yb_build.sh --java-test 'org.yb.pgsql.TestYbQueryDiagnostics#testPgssResetBetweenDiagnostics'

Reviewers: asaha

Reviewed By: asaha

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D39135

Author: IshanChhangani

src/postgres/contrib/pg_stat_statements/pg_stat_statements.c

@@ -1950,6 +1950,9 @@ pgss_store(const char *query, uint64 queryId,
 Datum
 pg_stat_statements_reset_1_7(PG_FUNCTION_ARGS)
 {
+	if (YBIsQueryDiagnosticsEnabled())
+		*yb_pgss_last_reset_time = GetCurrentTimestamp();
+
 	Oid			userid;
 	Oid			dbid;
 	uint64		queryid;