[FIX] P3: remove pycompat.{keys,items,values} helpers

Now that we're closer to switching to P3 for good, these helpers have
outlived their usefulness, and mostly add noise.

All remaining dict.iter*() or dict.view*() must be converted to the
normal keys(), values() or items() calls.

Whenever the result is likely to be used for more than the scope of a
loop, or when the dict needs to be modified during iteration, the calls
must be wrapped in a ``list()``, to protect the new P3 semantics.
Those cases are very exceptional.

Also removed some dead code or improved the API to remove unnecessary
conversions.

models/sale_coupon_program.py

@@ -4,7 +4,6 @@
 from odoo import api, fields, models, _
 from odoo.exceptions import UserError
 from odoo.tools.safe_eval import safe_eval
-from odoo.tools import pycompat
 
 
 class SaleCouponProgram(models.Model):
@@ -206,7 +205,7 @@ class SaleCouponProgram(models.Model):
         valid_programs = self.filtered(lambda program: not program.rule_products_domain)
         for program in self - valid_programs:
             ordered_rule_products_qty = sum(
-                qty for product, qty in pycompat.items(products_qties)
+                qty for product, qty in products_qties.items()
                 if program._is_valid_product(product)
             )
             # Avoid program if 1 ordered foo on a program '1 foo, 1 free foo'