[Backport #12050] [Fixes #12049] Adapt the SLD and XML upload forms to the new progress API

[giohappy]

Checklist

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[codecov]

Codecov Report

Merging #12075 (2f3afbb) into 4.2.x (d46e227) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##            4.2.x   #12075      +/-   ##
==========================================
- Coverage   63.17%   63.17%   -0.01%     
==========================================
  Files         877      877              
  Lines       52551    52551              
  Branches     6596     6596              
==========================================
- Hits        33200    33198       -2     
- Misses      17828    17831       +3     
+ Partials     1523     1522       -1