added loading indicator to edit config dialog

[saberlynx]

Adding loading indicator to spin for 500ms before dialog content is rendered.

Checklist:

• [] Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #1579 into gsa-8.0 will decrease coverage by 0.01%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           gsa-8.0    #1579      +/-   ##
===========================================
- Coverage     37.5%   37.48%   -0.02%     
===========================================
  Files          965      965              
  Lines        21980    21988       +8     
  Branches      6125     6126       +1     
===========================================
  Hits          8243     8243              
- Misses       12427    12434       +7     
- Partials      1310     1311       +1

Impacted Files	Coverage Δ
gsa/src/web/pages/scanconfigs/editdialog.js	8.19% <0%> (-0.58%)	⬇️

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