Feat/algorithm in statistics

[vincentsarago]

This PR adds thealgorithm options for /statistics endpoints

Internally we remove the usage of BaseReader.statistics() endpoint use the combination of BaseReader.preview() and ImageData.statistics() methods

# Before
from Reader(...) as src_dst:
    return src_dst.statistics(...)

# Now
from Reader(...) as src_dst:
    image = src_dst.preview(...)

    if post_process:
        image = post_process(image)

    return image.statistics(...)