Add sample_data module using pooch for example datasets

[swagat-mishra28]

This PR implements a sample_data module for ethology datasets.

It introduces a load_sample_tracking() function using the pooch
library to download example datasets, similar to how scikit-image
provides sample datasets.

This establishes the structure for future datasets once a GIN
repository is configured.

Changes:

• Added ethology/datasets/sample_data.py
• Exposed function via datasets/__init__.py
• Added pooch dependency

[swagat-mishra28]

Hi, it looks like the workflow for this PR is currently awaiting maintainer approval to run the CI checks. Please let me know if I should make any adjustments or if the workflow can be approved.

Thanks!

[swagat-mishra28]

Update

This PR has been updated to include basic tests for the new sample_data module.

The added tests verify:

• that load_sample_tracking() returns a valid path
• that the returned file path exists locally
• that repeated calls return the same cached dataset
• that the expected dataset filename is returned

These tests help ensure that the dataset loader behaves correctly and that the caching mechanism provided by pooch works as expected.

The goal of these tests is to improve reliability of the dataset loading utilities while keeping the implementation lightweight and aligned with the original purpose of this PR (introducing the sample_data module structure).