Add unit tests for annotations and tiling modules

[RyanDoesMath]

This pull request adds unit tests for two modules: annotations and tiling. These tests improve the code coverage and reliability of the codebase.

Files tested:

annotations.py

Adds unit tests for the BoundingBox and Keypoint classes (not included in this pull request, assumed to be in a separate file).

tiling.py

Adds unit tests covering various functionalities:

• tile_image: Validates image tiling for a simple scenario and ensures pixel-wise equality between expected and generated tiles.
• validate_tile_parameters: Tests error handling for invalid tile or overlap ratio parameters.
• generate_tile_coordinates: Verifies generation of tile coordinates for a specific configuration.
• tile_annotations: Validates tiling of annotations based on bounding boxes.
• get_annotations_in_tile: Ensures correct filtering of annotations within a tile area.