fix(core): col name from HTML shouldn't disappear in picker, fixes #1475

[ghiscoding]

• fixes issue Column title created from HTML element disappear after using Column/GridMenu Picker #1475
• when unselecting any column from ColumnPicker/GridMenu it was causing columns created from native HTML element to disappear, I'm not exactly sure why but it looks like if I clone the node before calling .appendChild then the problem no longer exists. For reference, the issue is from these lines

  slickgrid-universal/packages/common/src/core/slickGrid.ts

  Lines 1615 to 1616 in 185b6f9

  	const colNameElm = createDomElement('span', { className: 'slick-column-name' }, header);
  	this.applyHtmlCode(colNameElm, m.name as string);

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.8%. Comparing base (ad39b75) to head (9559bcf).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1476     +/-   ##
========================================
+ Coverage    99.8%   99.8%   +0.1%     
========================================
  Files         199     199             
  Lines       21714   21715      +1     
  Branches     6985    6986      +1     
========================================
+ Hits        21650   21651      +1     
  Misses         64      64             

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