fix(core): small UI regression causing column width to be smaller

[ghiscoding]

• partially rolling back a small change made in PR fix: incorrect grid container box size calculation border not showing #1961
• use Math.fround (float) instead of Math.floor (int) for column width calculations, it helps with some grids but not all of them

trying again to fix the issue shown below, this issue is only happening in some Chromium browsers, it's rare but it does show then it shows consistently and it never happens in Firefox. I'm assuming this issue is caused by Chrome miscalculating the width (possibly because of float precision) and when that happens the scrollbar shows too early. In the case below, our grid container is 800px, we remove 15px for scrollbar and so we have 785px left for the columns and it's supposed to fit perfectly... but for some reasons, some browsers show the scrollbar when it shouldn't

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.0%. Comparing base (4499f42) to head (5c19e86).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1973   +/-   ##
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  Coverage   100.0%   100.0%           
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  Files         195      195           
  Lines       35920    35920           
  Branches    10645    10647    +2     
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  Hits        35920    35920           

Flag	Coverage Δ
angular	100.0% <ø> (ø)
universal	100.0% <100.0%> (ø)

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