[youtube] Support for Unicode in titles? Cyrillic, Greek etc.

[bryc]

There are some videos of these titles, which fail to save the name in the resultant file:

Юрий Бучма - Чернобыль, год спустя
Ηλίας Ασβεστόπουλος - Μου Μίλησαν
Виктор Вуячич - Несколько Первых Слов
Γιάννης Σπανός - Μοναξιά

Instead we get titles such as:

" - -aiFG0KL28Fg.webm"
" - -cfFrSbZBtTA.m4a"
". - -zVobKZbSSZ0.webm"

It would be nice if it does not lose the title when downloaded!

[dstftw]

Duplicate of #5045.
This is intentional behavior for now. See #4787 for the rationale and #5527 for alternative solution discussions.