fix: (ListItem) - Fix endMedia to not be removed from DOM on mouseleave for ListItem

[musingh1]

Earlier, we were listening for mouseEnter and mouseLeave, maintaining the isHovering state and only showing the endMedia when the item is hovered. This breaks the scenarios where endMedia is a Popup. Once the Popup is triggered we want the content to stay even after the user leaves the list item (e.g. points to the popup content).
So now, if provided we will always render all the media's and in Teams theme control the display of endMedia, headerMedia etc through styles.

[codecov]

Codecov Report

Merging #278 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #278      +/-   ##
==========================================
+ Coverage   91.72%   91.77%   +0.05%     
==========================================
  Files          41       41              
  Lines        1341     1325      -16     
  Branches      172      194      +22     
==========================================
- Hits         1230     1216      -14     
+ Misses        107      105       -2     
  Partials        4        4

Impacted Files	Coverage Δ
src/components/List/ListItem.tsx	100% <ø> (+6.38%)	⬆️
src/components/Portal/Portal.tsx	96.29% <0%> (-1.86%)	⬇️
src/components/Status/Status.tsx	100% <0%> (ø)	⬆️

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[jurokapsiar]

@musingh1 the same would need to be done for focus state if the user is using keyboard. Would you mind adding following commit to the PR: feature/mukul/fix-listitem-styles...feat/listitem-focus-styles

or should we create a followup PR after this one is merged?

[kuzhelov]

lets address comments before merging that.

Also, there are couple problems appearing when List Item example is rendered in Docs:

• Received true for a non-boolean attribute selection. ..
• child in an array or iterator should have a unique "key" prop

Lets address them as well before merging (I may assist in that :).