Fix/Improve Loading Indicator

[swaterkamp]

• Fix showing Loading indicator at entities pages
• Redesign and brand the Loading indicator

Checklist:

• [ X ] Tests
• [ X ] CHANGELOG Entry

[codecov]

Codecov Report

Merging #1469 into gsa-8.0 will increase coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           gsa-8.0    #1469      +/-   ##
===========================================
+ Coverage    37.35%   37.36%   +<.01%     
===========================================
  Files          963      963              
  Lines        21815    21810       -5     
  Branches      6092     6090       -2     
===========================================
  Hits          8150     8150              
+ Misses       12368    12363       -5     
  Partials      1297     1297

Impacted Files	Coverage Δ
gsa/src/web/components/loading/loading.js	100% <ø> (ø)	⬆️
gsa/src/web/entities/page.js	6.52% <0%> (+0.33%)	⬆️

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