tests: Add a missing test for post-normalisation lowercasing in IDN

See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/4387#note_2269324

This adds a test to increase the code coverage of `nameprep()` in
`ghostutils.c`. It was previously missing coverage of the second
`tolower()` operation. The new test triggers this by using a Unicode
codepoint which cannot be converted to lowercase itself, but which
normalises (NFKC) to uppercase characters which can — a Unicode Roman
numeral.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

glib/tests/hostutils.c

@@ -56,6 +56,7 @@ static const struct {
   /* uppercase characters */
   { "EXAMPLE.COM", "example.com", FALSE, FALSE },
   { "\xc3\x89XAMPLE.COM", "xn--xample-9ua.com", TRUE, TRUE },
+  { "Ⅷ.com", "viii.com", TRUE, FALSE },
 
   /* unicode that decodes to ascii */
   { "\xe2\x93\x94\xe2\x93\xa7\xe2\x93\x90\xe2\x93\x9c\xe2\x93\x9f\xe2\x93\x9b\xe2\x93\x94.com", "example.com", TRUE, FALSE },