adding hpg training code (DO NOT MERGE)

[sayatmimar]

This PR adds the slurm sctipt to run multi compartment segmentation training in HPG. Along with this script, please create the following folders in segmentationschool directory:

TRAINING_data
output
pretrained_model

In addition, also create slurm_log.out file (touch slurm_log.out).

Finally, please update user and CODESDIR path.

Singularity container (.sif) is located in /orange/pinaki.sarder/shared_singularity_files.

To pull this branch on your local, run the following on your main branch (git checkout main):

git fetch origin
git branch -f hpg_training origin/hpg_training
git checkout hpg_training