[IMP] event: translate ics file to the frontend lang

This commit translate the ics file for an event to
the language chosen by the public user on the website.
For connected users, the ics file is translated to
the user's language.

Task-3199180

closes odoo/odoo#113528

Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>