When the payment views were updated with commit odoo/odoo@f7b8f075, a
hook was improperly renamed to `code`, which doesn't help to figure out
its purpose. This commit renames it to `provider_credentials` which
better fits its role.
While doing so, the view files are also renamed and/or split by model to
increase their readability.
closesodoo/odoo#102976
X-original-commit: 49d126d4fce18761d0261adac00e115b840b9b47
Related: odoo/enterprise#32662
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>