Introduce 'woocommerce_get_order_item_totals_excl_free_fees' filter

The new filter will allow plugins that add order item meta to choose to
display the free fee items on order details pages and emails.
introduces the wp_product_has_unique_sku() function
fixed the wc_product_has_unique_sku() function name
added woocommerce support information in system status page
introduces the wc_get_core_supported_themes() function
Merge pull request #5754 from claudiosmweb/5753-feature-system-status-theme-support

Add theme support to system status page
Merge pull request #5752 from claudiosmweb/feature-wc-check-for-unique-sku-function

Introduces the wc_product_has_unique_sku() function
pre_get_posts is an action
Merge pull request #5660 from tamarazuk/upstream

Introduce 'woocommerce_get_order_item_totals_excl_free_fees' filter