[IMP] test_themes, theme_test_custo: add new test theme for tests

This commit introduces a new theme for tests purpose.
The goal is to be able to create records and simulate a real use case
without only testing through unit tests in python.
For instance, with this commit, we now fully test:
- menu creation
- page creation
- new header & footer template
- new image shape & background shape

This will be extended later to be able to test other stuff too, maybe
like changing the website logo (not supported yet). Also, our existing
standalone test in themes should use this theme instead of nano to not
rely on a real theme that might change.

Courtesy of NMI as this theme is partly based on his job.

closes odoo/design-themes#586

Related: odoo/odoo#99099
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

theme_test_custo/data/menu.xml

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="utf-8"?>
+<odoo>
+
+<!-- Case 1: Create a new navbar menu -->
+<record id="menu_example_1" model="theme.website.menu">
+    <field name="name">Example 1</field>
+    <field name="sequence" type="int">20</field>
+</record>
+
+<!-- Case 2: Create child menu below a theme.website.menu -->
+<record id="menu_example_1_item_1" model="theme.website.menu">
+    <field name="name">Item 1</field>
+    <field name="url">/example</field>
+    <field name="parent_id" ref="menu_example_1"/>
+    <field name="sequence" type="int">21</field>
+</record>
+<record id="menu_example_1_item_2" model="theme.website.menu">
+    <field name="name">Item 2</field>
+    <field name="url">/example/item-2</field>
+    <field name="parent_id" ref="menu_example_1"/>
+    <field name="sequence" type="int">22</field>
+</record>
+<record id="menu_example_1_item_3" model="theme.website.menu">
+    <field name="name">Item 3</field>
+    <field name="url">/example/item-3</field>
+    <field name="parent_id" ref="menu_example_1"/>
+    <field name="sequence" type="int">23</field>
+</record>
+
+<!-- Case 3: Create a mega menu -->
+<record id="menu_products" model="theme.website.menu">
+    <field name="name">Mega Menu</field>
+    <field name="url">/mega-menu</field>
+    <field name="sequence" type="int">30</field>
+    <field name="mega_menu_content" type="html">
+        <section class="o_cc o_cc2 pt32 pb32">
+            <div class="container">
+                <div class="row">
+                    <div class="col-lg-3">
+                        <i class="fa fa-cube"/>
+                        <p>Text</p>
+                    </div>
+                    <div class="col-lg-3">
+                        <i class="fa fa-cube"/>
+                        <p>Text</p>
+                    </div>
+                    <div class="col-lg-3">
+                        <i class="fa fa-cube"/>
+                        <p>Text</p>
+                    </div>
+                    <div class="col-lg-3">
+                        <i class="fa fa-cube"/>
+                        <p>Text</p>
+                    </div>
+                </div>
+            </div>
+        </section>
+    </field>
+</record>
+
+<!-- Case 4: Create a new whole menu hierarchy (to be put elsewhere) -->
+<record id="main_menu_animals" model="theme.website.menu">
+    <field name="name">Main Menu Animals</field>
+    <field name="use_main_menu_as_parent" eval="False"/>
+    <field name="url">/main-menu-animals</field>
+</record>
+<record id="menu_dogs" model="theme.website.menu">
+    <field name="name">Dogs</field>
+    <field name="url">/dogs</field>
+    <field name="parent_id" ref="main_menu_animals"/>
+    <field name="sequence" type="int">10</field>
+</record>
+<record id="menu_cats" model="theme.website.menu">
+    <field name="name">Cats</field>
+    <field name="url">/cats</field>
+    <field name="parent_id" ref="main_menu_animals"/>
+    <field name="sequence" type="int">20</field>
+</record>
+
+</odoo>