WooCommerce Subscriptions 8.3.0

* Add: Support for ajax add-to-cart flows from the single product page, when upgrading or downgrading subscriptions.
* Add: Enhanced functionality from the WooCommerce Subscription Downloads plugin has now been integrated directly into WooCommerce Subscriptions.
* Fix: Ensured the subject line for the "Customer Renewal Invoice" email correctly updates.

* Fix: Prevent a fatal error that can occur when previewing emails in WooCommerce email settings.
* Fix: Prevent technical subscription-specific discount types from appearing in the coupon edit UI.
* Fix: Add admin notice and debug tool to recreate the payment retry database table when it's missing.
* Fix: Prevent resubscribe and reactivate buttons from showing for subscriptions containing disabled, deleted, draft, or limited products.
* Fix: Prevent error that blocks the subscriptions list from loading when gifted subscriptions are purchased with certain payment methods.
* Fix: Ensure gift recipient email address is displayed in the order confirmation email sent to the purchaser.
* Fix: Prevent pickup location options from displaying incorrectly alongside shipping methods on the Blocks Checkout page.
* Fix: Fix invalid HTML tags that cause fatal errors when using themes with WordPress Interactivity API.
* Fix: Add password reset links to the new account email template for gifted subscription recipients.
* Tweak: Improve the gift recipient email input field on Blocks Cart and Mini Cart to match the style of other checkout fields.
* Dev: Improve housekeeping of output buffers when handling requests to change subscription payment methods.
* Dev: Improve type safety in relation to the `wcs_get_subscription()` function.

* Add: Blocks Checkout now displays a single shipping method selection for both initial and recurring carts, similar to Classic Checkout. This can be disabled using the `wcs_cart_totals_shipping_html_price_only` filter.
* Fix: Resubscribing to a limited subscription from the product page will now reactivate the existing subscription.
* Fix: "New initial order - Recipient" email template preview no longer causes critical error.
* Fix: Shipping value on blocks checkout no longer shows as "Free" when no shipping method is available.
* Dev: Improved data telemetry which is sent to WooCommerce:
* WooCommerce Subscriptions setting values
* Order totals of subscription-related orders by order type and payment gateway, aggregated by month
* Number of subscription-related orders by order type and payment gateway, aggregated by month
* Number of products in parent subscription orders, aggregated by month
* Number of non-zero value parent subscription orders, aggregated by month
* Number of subscription products by billing interval
* Number of giftable subscription products
* Number of subscriptions by payment method, billing period, and renewal type
* Number of gifted subscriptions
* Number of subscribers
* Purchase event for subscription products
* Exclude orders with a "processing" status from the "subscription_orders" telemetry data.

* Add: REST API endpoint to retrieve subscriptions associated with a specific order ID.
* Fix: Keep subscription with successful renewals active when parent order fails.
* Fix: Error when renewing subscriptions with downloadable gifts.
* Fix: Improve performance by loading assets only when necessary.
* Fix: "Update cart" button being always enabled.
* Fix: Gifting recipient email layout issues when using a long e-mail address.
* Fix: Gifting checkbox not showing up on blocks cart when using WooCommerce 10.2+.
* Fix: Deleting a gifted subscription recipient will not delete their subscriptions, they will be moved to the subscription purchaser instead.
* Dev: The `wcs_get_subscriptions()` and `wcs_get_subscriptions_for_order()` functions are now stricter, and only return instances of `WC_Subscription`.