## Impacted versions:
 8.0 / 9.0 / 10.0
## Steps to reproduce:
* see https://github.com/odoo/odoo/issues/11841
* in a shell
  1. create an in memory record `order = self.env['purcahse.order'].new({....})`
  2. create an in memory record with a reference to the first one `order_line = self.env['purchase.order.line'].new({'order_id': order, ....})`
  3. order_line.order_id is an in memory recordset
  4. create a record for a model that inherits from mail.thread `self.env['product.product'].create({....})`
  5. At this stage order_line.order_id is an empty recordset

## Current behavior:
 In memory records are dropped when a call is done to self.invalidate_cache
## Expected behavior:
In memory records are preserved when a call is done to self.invalidate_cache


There are lot of places where the method `invalidate_cache` is called and the silent removal of the in memory records from all environments has unpredictable effects on fields modified by a computed method or an onchange or even related fields .... Moreover since all caches are invalidated each time you create / write / unlink  (https://github.com/odoo/odoo/blob/10.0/addons/mail/models/mail_followers.py#L111) an instance of a model that inherits from 'mail.thread', the performances of the server are severely penalized.

OPW703903

uom_id = procurement.product_id.uom_po_id.id
        qty = uom_obj._compute_qty(cr, uid, procurement.product_uom.id, procurement.product_qty, uom_id)
        if seller_qty:
            qty = max(qty, seller_qty)
        price = pricelist_obj.price_get(cr, uid, [pricelist_id], procurement.product_id.id, qty, partner.id, dict(context, uom=uom_id))[pricelist_id]
        
        new_context = context.copy()
        new_context.update({'lang': partner.lang, 'partner_id': partner.id})
        product = prod_obj.browse(cr, uid, procurement.product_id.id, context=new_context)
        taxes_ids = procurement.product_id.supplier_taxes_id
        taxes_ids = taxes_ids.filtered(lambda x: x.company_id.id == procurement.company_id.id)
        
        fiscal_position = False
        fiscal_position_id = po_obj.onchange_partner_id(cr, uid, None, partner.id, context=dict(context, company_id=procurement.company_id.id))['value']['fiscal_position']
        if fiscal_position_id:
            fiscal_position = acc_pos_obj.browse(cr, uid, fiscal_position_id, context=context)
        taxes = acc_pos_obj.map_tax(cr, uid, fiscal_position, taxes_ids, context=context)
        name = product.display_name
        if product.description_purchase:
            name += '\n' + product.description_purchase
        return {
            'name': name,
            'product_qty': qty,
            'product_id': procurement.product_id.id,
            'product_uom': uom_id,
            'price_unit': price or 0.0,
            'date_planned': schedule_date.strftime(DEFAULT_SERVER_DATETIME_FORMAT),
            'taxes_id': [(6, 0, taxes)],
        }
    def _calc_new_qty_price(self, cr, uid, procurement, po_line=None, cancel=False, context=None):