Improve segments processing in sits_classify

[OldLipe]

Describe the requested improvement
Improve segment parallelization and processing with single-chunk cubes.
Currently, we divide segments into chunks. However, this takes a long time when the cubes have small chunks.
First, we need to check the chunk size and then split the segments.

Associated sits API function

data_dir <- system.file("extdata/raster/mod13q1", package = "sits")
# create a data cube
cube <- sits_cube(
    source = "BDC",
    collection = "MOD13Q1-6.1",
    data_dir = data_dir
)
# segment the vector cube
segments <- sits_segment(
    cube = cube,
    output_dir = tempdir()
)
# create a classification model
rfor_model <- sits_train(samples_modis_ndvi, sits_rfor())
# classify the segments
seg_probs <- sits_classify(
    data = segments,
    ml_model = rfor_model,
    memsize = 1,
    output_dir = tempdir(),
    version = "v2"
)
# label the probability segments
seg_label <- sits_label_classification(
    cube = seg_probs,
    output_dir = tempdir()
)