[FIX] website_sale_order_type: speed up tour

Without this patch, it's easy that the tour fails randomly due to a timeout when generating the sales order report. These assets can take a long time, increasing when more addons are installed.

In an integrated database, this patch makes the test go from this log:

    2020-11-06 10:34:53,941 34 INFO devel werkzeug: 127.0.0.1 - - [06/Nov/2020 10:34:53] "POST /payment/transfer/feedback HTTP/1.1" 302 - 730 4.368 11.800

To this one:

    2020-11-06 10:32:55,517 34 INFO devel werkzeug: 127.0.0.1 - - [06/Nov/2020 10:32:55] "POST /payment/transfer/feedback HTTP/1.1" 302 - 479 2.906 5.771

That's about 50% the time.

In the same patch, I remove the `self.env` patch that was only needed for Odoo v11 and lower.

website_sale_order_type/tests/test_website_sale_order_type.py

@@ -8,7 +8,6 @@ class TestFrontend(HttpCase):
 
     def setUp(self):
         super(TestFrontend, self).setUp()
-        self.env = api.Environment(self.registry.test_cr, self.uid, {})
         self.sale_type_model = self.env['sale.order.type']
 
         self.partner = self.env.ref('base.partner_admin')
@@ -42,6 +41,17 @@ def create_sale_type(self):
     def test_website_sale_order_type(self):
         self.partner.sale_type = self.sale_type
         existing_orders = self.env['sale.order'].search([])
+        # Precreate SO report assets cache to avoid tour step timeouts
+        views = (
+            "web.assets_common",
+            "web.report_assets_common",
+            "web.report_assets_pdf",
+        )
+        for view in views:
+            self.env["ir.qweb"]._get_asset_nodes(
+                view, self.env.context, js=False)
+            self.env["ir.qweb"]._get_asset_nodes(
+                view, self.env.context, css=False)
         # In frontend, create an order
         tour_prefix = "odoo.__DEBUG__.services['web_tour.tour']"
         self.phantom_js(