/series/add: consider using details with summary as a replacement to links and divs

[php-coder]

Idea from Pavel Finkelshtein (@asm0dey): instead of using JS code and chevrons for hiding parts of the form, it's better to use a pure CSS approach with <details>/<summary> tags: http://jsfiddle.net/thurstanh/emtAm/2/ It won't work in IE but it's OK because in this case all the parts will be visible.

[php-coder]

The old code is causing test flakes (like #556) because sometimes the block is visible and sometimes it's not. After fixing #565 the code for hiding/showing elements has started to use height(0) that seems causes flakes because zero height passes Wait Until Element Is Visible check.

[php-coder]

Could be related: https://habr.com/ru/post/477520/