WooCommerce Subscriptions 6.9.0

* Fix: Fix an issue with the release date of 2.4.6

* Dev: Add 'woocommerce_subscription_is_manual' filter. PR#3102
* Tweak: Add action attributes to the add to cart form on subscription product pages. PR#3105
* Fix: Remove "Your subscription will be activated when payment clears" on the order received page when the subscription is already active. PR#3099
* Fix: [WP 5.0.2] Fix an issue where the Admin Subscriptions table was empty.

* Fix: Fix caching on data for the Upcoming Recurring Revenue and Subscriptions By Date reports. PR#3069.
* Fix: Fix compatibility with Disable Report Cache Updates mini-plugin. PR#3069.
* Fix: Make Stripe source ID unique while setting through REST API. PR#3090.
* Fix: Display synced variation product's next payment date after the variation is selected by a customer on the product page. PR#3094.
* Fix: Activate subscription after processing an IPN on parent orders previously processed by PDT. PR#3097.
* Tweak: Update incomplete retry migration status label styling and wording to "In-Progress" to avoid confusing in-progress migrations as being a problem. PR#3088