✨ feat: add custom hitboxes and rework related modules

[aksiome]

Description

This PR introduces a major overhaul to how hitboxes are defined and handled in Bookshelf. Given the size and impact of this update, a thorough review and additional testing are needed.
Even though this is still a draft, @theogiraudet, I'd appreciate an early review of the API design. If anything feels unclear, misnamed, or could be improved from a usability or consistency standpoint, please flag it.

Related Issues

• Fixes Raycast doesn't always stop at the nearest contact point when using both blocks and entities #457
• Fixes Add bs.width and bs.height scores to move and raycast #442
• Fixes Optimize and improve bs.move, bs.raycast and bs.hitbox #440
• Fixes Add a way to define custom hitboxes #329

Additional Notes

Remaining tasks:

• Update the changelog (mark deprecated elements clearly)
• Rework hitbox check functions to use the new system and update docs accordingly
• Check feature metadata update date

Tasks to complete before merging

• I agree to release my contribution under the MPL v2 License.
• My pull request is associated with an existing issue.
• I have updated the changelog to reflect my contribution.
• If this pull request adds or modifies a feature:
  • I have documented my changes in the /docs folder.
  • I have updated the metadata of the feature. See feature metadata.
  • I have thoroughly tested my changes. See testing guidelines.