Implement LP++ for better linear probing results

[mehdidc]

Implement "lp++: A Surprisingly Strong Linear Probe for Few-Shot CLIP" (https://openaccess.thecvf.com/content/CVPR2024/papers/Huang_LP_A_Surprisingly_Strong_Linear_Probe_for_Few-Shot_CLIP_CVPR_2024_paper.pdf), a strong linear probing baseline