Event: Stop shimming focusin & focusout events

Event: Stop shimming focusin & focusout events

Latest versions of all browsers now implement focusin & focusout natively
and they all converged on a common event order so it doesn't make much sense
for us to normalize it to a different order anymore.

Note that it means we no longer guarantee that focusin fires before focus
and focusout before blur.

Fixes gh-4300
Closes gh-4362