Avoid running query in WC_Payments::should_load_stripe_billing_integration() on every page load

[prettyboymp]

The fallback query used in WC_Payments::should_load_stripe_billing_integration() currently runs on every page load. The decision from the query results should probably be cached, especially since it isn't a simple query and isn't extremely fast.

woocommerce-payments/includes/class-wc-payments.php

Lines 2067 to 2080 in faf5ef7

	$result = wcs_get_orders_with_meta_query(
	[
	'status' => 'any',
	'return' => 'ids',
	'type' => 'shop_subscription',
	'limit' => 1, // We only need to know if there are any - at least 1.
	'meta_query' => [ // phpcs:ignore WordPress.DB.SlowDBQuery.slow_db_query_meta_query
	[
	'key' => '_wcpay_subscription_id',
	'compare' => 'EXISTS',
	],
	],
	]
	);

Resulting Query:

SELECT wp_wc_orders.id FROM wp_wc_orders INNER JOIN wp_wc_orders_meta AS meta0 ON ( wp_wc_orders.id = meta0.order_id ) WHERE 1=1 AND (wp_wc_orders.status IN ('wc-pending','wc-active','wc-on-hold','wc-cancelled','wc-switched','wc-expired','wc-pending-cancel')) AND (wp_wc_orders.type = 'shop_subscription') AND ((meta0.meta_key = '_wcpay_subscription_id')) GROUP BY wp_wc_orders.id ORDER BY wp_wc_orders.date_created_gmt DESC LIMIT 0, 1

Query explain:

+----+-------------+--------------+--------+---------------------------------------------+----------------+---------+-------------------------+------+---------------------------------------------------------------------+
| id | select_type | table        | type   | possible_keys                               | key            | key_len | ref                     | rows | Extra                                                               |
+----+-------------+--------------+--------+---------------------------------------------+----------------+---------+-------------------------+------+---------------------------------------------------------------------+
| 1  | SIMPLE      | meta0        | ref    | meta_key_value,order_id_meta_key_meta_value | meta_key_value | 258     | const                   | 1    | Using index condition; Using where; Using temporary; Using filesort |
| 1  | SIMPLE      | wp_wc_orders | eq_ref | PRIMARY,status,type_status,type_status_date | PRIMARY        | 8       | wpmu_d05.meta0.order_id | 1    | Using where                                                         |
+----+-------------+--------------+--------+---------------------------------------------+----------------+---------+-------------------------+------+---------------------------------------------------------------------+