Fix Key Array Caching

[hang-yin]

Thanks to @MhdMohammadi for reporting this.

Problem

In instance segmentation, Replicator occasionally mislabels some objects as unlabelled in the info dict despite having distinct labels for them in the segmentation map. This typically occurs when only a small portion (a few pixels) of an object is visible.

The issue impacts our key array caching in segmentation remapping:

1. We only update the key array when new labels appear.
2. We don't revisit and update previously assigned keys.

Consequently, even after moving the camera and Replicator providing correct labels for these previously "unlabelled" objects, our key array fails to update this information and continues to mark them as "unlabelled".

Proposed Solution

1. Internally track keys marked as "unlabelled".
2. For each new segmentation map:
   a. Check if any tracked "unlabelled" keys have been assigned valid labels.
   b. If so, retrospectively update our key array to reflect the new, valid label.