[FW][FIX] base: make parent contact lang prevail on DB lang

With commit odoo/odoo@83ffe8b we ensured that while creating a child contact, it
takes language from its parent by default if any, otherwise falls back to DB
lang.

The fix was done with help of `default_get` method. However after merge of
odoo/odoo#55995 `default_get` is now called through the onchange for o2m
fields. Now we don't get the default value of `parent_id` here which
re-introduced the bug.

This commit fixes the behavior by setting the language from onchange
while creating the child contact and thus (once again) making the
language from parent contact prevail on DB lang.

We also re-use default_lang coming from parent in form view, which partially
reverts odoo/odoo@83ffe8b .

TaskID-2416922

closes odoo/odoo#72960

X-original-commit: 4d9b85bd07e487e7843dc458332dede36c2889c2
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

odoo/addons/base/views/res_partner_views.xml

@@ -234,7 +234,7 @@
 
                     <notebook colspan="4">
                         <page string="Contacts &amp; Addresses" name="contact_addresses" autofocus="autofocus">
-                            <field name="child_ids" mode="kanban" context="{'default_parent_id': active_id, 'default_street': street, 'default_street2': street2, 'default_city': city, 'default_state_id': state_id, 'default_zip': zip, 'default_country_id': country_id, 'default_lang': None, 'default_user_id': user_id, 'default_type': 'other'}">
+                            <field name="child_ids" mode="kanban" context="{'default_parent_id': active_id, 'default_street': street, 'default_street2': street2, 'default_city': city, 'default_state_id': state_id, 'default_zip': zip, 'default_country_id': country_id, 'default_lang': lang, 'default_user_id': user_id, 'default_type': 'other'}">
                                 <kanban>
                                     <field name="id"/>
                                     <field name="color"/>