feat(expr): implement dummy pg_stat_get_numscans function (#15642)

Signed-off-by: Runji Wang <[email protected]>

Author: wangrunji0408

src/frontend/src/binder/expr/function.rs

@@ -1300,6 +1300,7 @@ impl Binder {
                 ("pg_get_partkeydef", raw_literal(ExprImpl::literal_null(DataType::Varchar))),
                 ("pg_encoding_to_char", raw_literal(ExprImpl::literal_varchar("UTF8".into()))),
                 ("has_database_privilege", raw_literal(ExprImpl::literal_bool(true))),
+                ("pg_stat_get_numscans", raw_literal(ExprImpl::literal_bigint(0))),
                 ("pg_backend_pid", raw(|binder, _inputs| {
                     // FIXME: the session id is not global unique in multi-frontend env.
                     Ok(ExprImpl::literal_int(binder.session_id.0))