[RASTER][Feature] Applying scale and offset to raster data - funded Ifremer

An issue has been opened 6 mounth ago
[BUG] #8417 incorrect value loaded from netcdf file
The data has not be loaded incorrectly, but QGIS doesn't apply scale
and offset defined for each band.

This commit will apply scale and offset to GDAL Provider BandStatistics
and to RASTER block of data.

This new pull request integrates reviews from @blazek @wonder-sk @etiennesky and @timlinux :
* integrated and updated the test provided by @etiennesky
* updated the sip API for un-protected method requested by @wonder-sk
* updated the stats method to account for negative scale value