WooCommerce Subscriptions 6.9.0

* Tweak: Improve the missing customer error message displayed for third-party built checkouts when registration is disabled on checkout.
* Fix: Remove the possibility of a negative calculation of prepaid days on subscription downgrades.
* Fix: Fix issues preventing stores using the $0 Initial Checkout feature from being able to checkout.
* Fix: Remove potential fatal error when processing end-of-prepaid term scheduled actions caused by the subscription not existing.
* Fix: Trigger payment complete actions after renewing early via modal.
* Fix: Performance improvements to limited products running slow queries on the shop page.
* Fix: [PHP 8.0] Only pass array values to call_user_func_array calls.
* Fix: [PHP 8.0] Replaces certain uses of method_exists() with is_callable().

Uploaded correct file (thanks @rafola )

* Fix: Store shipping line item instance ID separately and copy it to renewal line item meta. PR#3712
* Fix: Account for the base store tax rates subtracted from line items when paying for renewals manually. PR#3745
* Fix: Update the persistent cart while paying for renewal orders via the checkout. Fixes division by zero errors while manually renewing. PR#3824
* Fix: Clear report cache data before regenerating new preset date results preventing infinitely growing report caches. PR#3800
* Fix: Remove subscription period string transient caching to fix issues after translating. PR#3770
* Fix: WC 4.7 compatibility. Use filter to change endpoint titles in My Account. PR#3857
* Fix: When generating product price strings fallback to a default period string if no period is set. PR#3848
* Fix: Remove uses of jQuery( document ).ready() which was deprecated. PR#3846
* New: Add option to enable admin to lock in increased parent order line item prices. PR#3816
* Tweak: Allow admin to set a next payment date in 2 minutes via the edit subscription screen on staging sites. PR#3778