[IMP] base: add vat_label to New Zealand

VAT in New Zealand is called GST. New Zealand entities are issued IRD numbers and when registered for tax their IRD number is used as GST number.

> from: https://www.business.govt.nz/tax-and-accounting/basic-tax-types/gst

> For sole traders, your GST number will be the same as your IRD number.
> For partnerships and companies, it’s the same as your partnership or company IRD number.

GST number is legally required on all tax invoices (https://www.ird.govt.nz/gst/tax-invoices-for-gst/how-tax-invoices-for-gst-work)

I have added the VAT label as IRD/GST so that it's clear wherever else VAT label is used that the same number fits both contexts (rather than introducing a second field for identical data through NZ l10n).

closes odoo/odoo#109800

X-original-commit: 8ac78c222ae93e000a43c71ac9e359a8542f8cff
Signed-off-by: Josse Colpaert <jco@odoo.com>

odoo/addons/base/data/res_country_data.xml

@@ -1091,6 +1091,7 @@
             <field name="code">nz</field>
             <field name="currency_id" ref="NZD" />
             <field eval="64" name="phone_code" />
+            <field name="vat_label">IRD/GST</field>
         </record>
         <record id="om" model="res.country">
             <field name="name">Oman</field>