Support unicode character for `initcap` function

[tlm365]

Is your feature request related to a problem or challenge?

Make initcap function work with Unicode character.

Describe the solution you'd like

Current behavior of DataFusion:

select initcap('đẹp đẽ êm ả édouard'); --đẹP đẽ êM ả éDouard
select initcap('ñandú árbol éxito'); --ñAndú áRbol éXito
select initcap('олег иванович'); --олег иванович
select initcap('íslensku þjóðarinnar'); --íSlensku þJóðArinnar
select initcap('ελληνική επιστήμη'); --ελληνική επιστήμη

Expected behavior: (Postgres)

select initcap('đẹp đẽ êm ả édouard'); --Đẹp Đẽ Êm Ả Édouard
select initcap('ñandú árbol éxito'); --Ñandú Árbol Éxito
select initcap('олег иванович'); --Олег Иванович
select initcap('íslensku þjóðarinnar'); --Íslensku Þjóðarinnar
select initcap('ελληνική επιστήμη'); --Ελληνική Επιστήμη

Describe alternatives you've considered

No response

Additional context

Found in comment of @Dandandan

[tlm365]

take