We now buffer the request for the input to a resample filter by
a variable number of pixels (depending on the resampling type)
in order to fetch the neighbouring pixels to the edges of individual
raster blocks. This allows the resampling to utilise these
neighbouring pixels when resampling the edges of tiles, avoiding
discrepancies and rendering artifacts over the borders of
raster tiles.
Fixes#30152
which doesn't require pre-allocation of a temporary QImage
The existing interface is very inefficient for the bilinear resampler,
because it requires allocation of a temporary QImage just to pass
the desired height and width to the resampler...
