The primary goal of this PR is to finalize the unification of product pricing across Odoo Enterprise by migrating the Rental and Subscription applications to the core pricelist engine. This change eliminates legacy, app-specific pricing models in favor of a centralized and more capable architecture.

This consolidation integrates Subscription and Rental pricing directly into the unified *Prices* tab introduced in the base module. For Subscriptions, recurring prices are now managed alongside standard rules. For Rental, the rigid `product.pricing` model and legacy configuration settings (such as static delay fines) are removed. Instead, users define rental prices using standard pricelist items, supported by a new `periodicity` configuration (Hours, Days, Weeks, Nights) on the product form.

On a technical level, the rental engine has been refactored to leverage the full capabilities of the pricelist system, enabling previously unavailable features like formula-based pricing and variant specific extra-price. The eCommerce frontend has been updated to support this dynamic logic, ensuring that availability constraints, periodicity display, and price computations are consistent with the new backend architecture.

task-5375343

Co-authored-by: Lionel Piraux <lipi@odoo.com>
Co-authored-by: Victor Feyens <vfe@odoo.com>
Co-authored-by: Louis Tinel <loti@odoo.com>