fix(ngAnimate): fire callbacks when document is hidden

Since commit a3a7afd3aa70d981b0210088df53fa2cf68d3a3d, animations are not run
when the document is hidden (only their structural or class change effects are executed).
However, some libraries rely on the $animate.on() callbacks to be called even when no actual animation
runs.
This commit restores the behavior for the ngAnimate.$animate functions.
Note that callbacks still won't be called if animations are disabled, because this would be be a potential
breaking change, as some applications might rely on this implementation.

Fixes #14120