Tiered Pricing Table for WooCommerce 6.4.0

* Fix: Do not remove "step" attribute from qty field when variation is reset - some there use it to make +\- buttons work.
* Update: Increase performance by do not check each child of variable product for tiered pricing on product page load.
* Update: Remove "product has no rules" checkbox from variable product advanced settings.
* Fix: Issue when global pricing rules didn't save tiered pricing applying type. (mix&match or individual)

* New: New global pricing rules form
* New: Maximum and "group of quantity" quantity options
* New: Percentage discounts for regular prices for role-based pricing rules
* New: Gutenberg blocks for tiered pricing
* New: Base unit name per product
* New: Custom columns for pricing table
* New: "You save" feature
* New: Notice when tiered pricing is set incorrectly
* New: Debug mode
* New: Minimum PHP version is 7.2
* New: Yith request a quote integration
* New: Calculation logic settings
* Update: Codebase redesign
* Update: Settings page updated
* Update: Redesigned tiered pricing for manual orders
* Update: Cache and performance updates
* Fix: a bunch of minor issues

* Fix: fatal error with cart upsell on the cart