SelectField is laggy when the number of items is very large

[gabro]

For example, if you have a SelectField with all the countries in the world, then it starts to lag.

This is due to the lack of virtualization in react-select, see JedWatson/react-select#3128 and JedWatson/react-select#2850 for more info.

Judging from those threads, a promising solution would be to have a custom MenuList built on top of react-virtualized's List

[marcopiii]

I reproduced the bug in this playroom