Fix compilation warnings

[rolalaro]

Fix compilation warnings on Windows in the class vpImageFilter
Fix some warnings detected by SonarQube

[codecov]

Codecov Report

Attention: 62 lines in your changes are missing coverage. Please review.

Comparison is base (e4338fe) 54.43% compared to head (3855247) 54.42%.
Report is 5 commits behind head on master.

Files	Patch %	Lines
modules/core/include/visp3/core/vpImageFilter.h	83.41%	33 Missing ⚠️
modules/core/src/image/vpImageFilter.cpp	44.00%	28 Missing ⚠️
modules/core/src/image/vpImageConvert.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1289      +/-   ##
==========================================
- Coverage   54.43%   54.42%   -0.01%     
==========================================
  Files         400      400              
  Lines       50514    50516       +2     
==========================================
- Hits        27496    27495       -1     
- Misses      23018    23021       +3     

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