Respect extent and res element type in rasterize/resample

[tiemvanderdeure]

To follow up on some discussion in #852

Currently in rasterize and resample, if the user provides an extent as to, the resulting dimensions are always Float64 regardless of the element type of the input extent and resolution.

E.g.

using Rasters, Extents, ArchGDAL
ext = Extent(X = (1, 10), Y = (1, 10))
ras1 = rasterize((1,1), to=ext, res=1, fill=1, reducer=sum)
ras2 = resample(rasr, to=ext, res = 1)
dims(ras1)

At least for rasterize this is a conversion happening in Rasters._extent