Knn implementaiton and downstream fix

[OguzAtaCal]

• Added knn evaluation and all related files
• Fixed class number error for organsmnist
• Fixed id_linear script and main so vit checkpoints are properly loaded for evaluation
• Added a script that deletes any row containing "vit" from downstream_results.csv
• Improved id_downstream.sh so that it skips any runs with results inside the downstream_results.csv

[kivanctezoren]

Let's keep in mind that the .csv check in the bash script prevents restarting our previous erroneous vit_small runs (the oneswhich actually used rn50). Command that removes every line containing vit_small:

Verify: sed '/vit_small/d' ./downstream_results.csv Execute: sed -i '/vit_small/d' ./downstream_results.csv