**Description of the issue/feature this PR addresses:**

Adds minimal stock functionality to the Sale, and Purchase module without needing to install the stock module. 
A user can now track the quantity on hand of a product, which we deduct from when making a sale and we add to when making a purchase. This is done without pickings or deliveries, solely using the `qty_received` and `qty_delivered` fields on the order lines.

**WHY:**  You have to install stock module to handle your quantity on hand in Odoo. However the stock module enforce hard process with deliveries and receipts to fill and validate. A lot of business don't have the requirement of an advanced inventory management and they just want to increase/decrease the inventory with simple operations base on their sales/purchase/POS,...

**Current behavior before PR:**
Cannot track available quantities for product without installing stock.

**Desired behavior after PR is merged:**
A user should be able to:

 - Define product qty in stock
 - See product availability on SO line
 - Reduce the quantity by delivering product on SO line 
 - Increase the qty in stock be receiving product on PO line
 - See incoming / outgoing quantities per product 

Because the new feature relies heavily on keeping your delivered / received qty up to date, we also included some buttons to make it easier to keep up to date (Deliver/Receive buttons on the PO/SO form and list) and we display the incoming and outgoing qty on the product smart button as well. 

Upgrade PR: https://github.com/odoo/upgrade/pull/9081
task#5186344

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