Add EmbeddingCollapseMetric: detect representational collapse in medical imaging embeddings

Closes #8808

Signed-off-by: ekansh-arora0 <ekansh.arora0@gmail.com>

Author: ekansh-arora0

monai/metrics/__init__.py

@@ -17,6 +17,7 @@
 from .confusion_matrix import ConfusionMatrixMetric, compute_confusion_matrix_metric, get_confusion_matrix
 from .cumulative_average import CumulativeAverage
 from .f_beta_score import FBetaScore
+from .embedding_collapse import EmbeddingCollapseMetric, compute_embedding_collapse
 from .fid import FIDMetric, compute_frechet_distance
 from .froc import compute_fp_tp_probs, compute_fp_tp_probs_nd, compute_froc_curve_data, compute_froc_score
 from .generalized_dice import GeneralizedDiceScore, compute_generalized_dice