[Refactor] Improve understandability and usability of imports

[apirrone]

For ex, instead of

from vision_models.mobile_sam.mobile_sam_wrapper import MobileSamWrapper

do

from vision_models.object_segmentation.mobile_sam import MobileSamWrapper

Or ideally

from pollen_vision.object_segmentation import MobileSam
from pollen_vision.object_detection import OwlVit

[apirrone]

Closed by #79