Display idn in both ascii and unicode forms

[hannaeko]

Purpose

Following 2023.2 release IDN are always normalized in ASCII in database, to be more user friendly this PR convert them back to unicode to be displayed on the result page. It also displayed the ASCII form in bracket.

This changes nothing for non-IDN.

Context

Fixes #198

Changes

• Always convert domain to their Unicode form in title and result heading
• Also display ASCII domain for IDN
• The file name of the exported result uses the ASCII domain

How to test this PR

Ideally make the test using a backend < 2023.2 and with backend >= 2023.2, to see how it behaves when the returned domain is in ASCII and Unicode, and check that both should behave the same way.

• Display the result of a test of an IDN
• The page title must contain the Unicode domain
• The result heading must show both the Unicode and ASCII domains