Per 346 raindrop training config

[onionlai]

Description

List of changes incorporated in this PR:

• Register the RaindropsOnWindshield dataset class, and includes a draft for GlydLensArtifactDataset (for future use).
• Add training configs for the RaindropsOnWindshield dataset, covering the following models: BiSeNet v1, BiSeNet v2, DeepLab v3+, and Fast-SCNN.
• Implement a custom visualization hook for displaying a subset of images during validation runtime.
• Add helper utilities for feature map visualization
• Temporarily fix version constraint to avoid mmcv version conflict (works)