ip link add name $'d\xccf\\c' type dummy

Use nm_utils_str_utf8safe_escape() to sanitize non UTF-8 sequences
before exposing them on D-Bus. The operation can be reverted client
side via nm_utils_str_utf8safe_unescape() or simply g_strcompress().

Note that this preserves all valid UTF-8 sequences as-is, with exception
of the backslash escape character and ASCII control characters. Thus, this
is a change in behavior for strings that contain such characters.

Note that nmcli is not changed to somehow unescape the string before
printing. As the string is not valid UTF-8 (or contains ASCII characters
that need escaping), they are not printable as-is, so unescaping before
printing makes little sense.