[FIX] l10n_multilang: translate country states name

Countries with several official languages often have multiple names for their
states. Allow to translate the state name for such countries.

Some monolingual countries but, yet, with a need of translation of the addresses
such as China or Germany can add the same flag in their respective l10n_* module

Closes #19481
Closes #20259

addons/l10n_multilang/models/account.py

@@ -69,3 +69,9 @@ class AccountAnalyticAccount(models.Model):
     _inherit = 'account.analytic.account'
 
     name = fields.Char(translate=True)
+
+
+class ResCountryState(models.Model):
+    _inherit = 'res.country.state'
+
+    name = fields.Char(translate=True)