Add AmazonComputers and AmazonPhoto graph datasets

[Uneeb808]

This PR adds support for the Amazon Co-purchase Network dataset.

Dataset includes:

• amazon_electronics_computers
• amazon_electronics_photo

Features:

• Dataset registration using DataDeps
• NPZ loading support
• Graph structure with node features and labels

Source:
https://github.com/shchur/gnn-benchmark

This dataset is commonly used for benchmarking Graph Neural Networks.

Related to #239

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.95%. Comparing base (3d40a68) to head (af9fa43).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #249      +/-   ##
==========================================
+ Coverage   45.94%   46.95%   +1.01%     
==========================================
  Files          50       53       +3     
  Lines        2501     2626     +125     
==========================================
+ Hits         1149     1233      +84     
- Misses       1352     1393      +41     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Uneeb808]

Hi! I'm Uneeb, a student interested in contributing to JuliaML for GSoC 2026.

This is my first contribution to the project. I added support for the Amazon Co-purchase Network dataset.

I’d really appreciate any feedback on this PR. I'm also interested in contributing more datasets or other improvements aligned with the GSoC project ideas.

Please let me know if there are other priority tasks I could help with. Thanks!

[CarloLucibello]

Thanks for the contribution!