fix(Portal): fix target for mouseEnter/mouselLeave events

[layershifter]

Fixes #3514.
Fixes #3508.

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Fix issues with invalid target for mouseEnter & mouseLeave events, also switches to a new EventStack API.

[codecov-io]

Codecov Report

Merging #3515 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3515      +/-   ##
==========================================
- Coverage   99.82%   99.82%   -0.01%     
==========================================
  Files         172      172              
  Lines        2804     2794      -10     
==========================================
- Hits         2799     2789      -10     
  Misses          5        5

Impacted Files	Coverage Δ
src/addons/Portal/Portal.js	100% <100%> (ø)	⬆️

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