* fix: resolve product variation type when the node is a base Post model
A cart item's variation node can be loaded through the generic post loader (e.g. under Polylang, which doesn't manage the product_variation post-type), arriving as a base \WPGraphQL\Model\Post that has no get_type(). resolve_product_variation_type() then fatals. Fall back to resolving the variation's product type from its ID via wc_get_product() when get_type() isn't callable.
* chore: remove stray graphql_debug() from ProductWithPricing price resolver
* test: disable Customer Note email so order-note tests aren't polluted by the WC email-sent note
* test: cover product-variation type fallback when the node loads as a base Post model
* - remove several fields that are already registered by core when the post type is mapped to the schema
* devops: Tests updated and coupon "salt" restored
* chore: Linter & PHPStan compliance met
* chore: Linter & PHPStan compliance met
* devops: "self" replaced with "static" in cli tests
* chore: fix cleanup after rebasing
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Co-authored-by: Geoff Taylor <geoff@axistaylor.com>
