[IMP] purchase: make billing consitent with sale invoicing

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Purpose
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Currently, purchase missing some billing functions that we have in sale
invoicing:
 - Create credit note when necessary
 - Create vendor bill in batch in list view

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Spec
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 - In case of retures, when create a bill for a purchase order, we check
the total amount we want to bill to decide whether it's a vendor bill or
a credit note.
 - In the list view, add a new action to create vendor bill/credit note
for all selected order.

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Links
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Task 2170715
PR #44210

Related: odoo/upgrade#919
Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>