feat: add key_line_3d and key_point_3d annotation objects and structures

[nehalmamgain]

This PR unblocks the DGP loader for 3D lane detection. It adds the necesary structures for KeyLine3D and KeyPoint3D, along with tests.

---

This change is 

[nehalmamgain]

CC: @wadimkehl P.S. I've requested @tk-woven for support on merge (PR needs at least 1 approval).

[nehalmamgain]

Thanks for your review! Making the changes.

Is there a way to reduce the file size from its current 1.2 MB and still have the image be useful? Basically as small as possible is preferred.

Let me just remove the image. The tests are for checking loading annotation, not loading images (those tests exist on this repo) so the image isn't needed.

[nehalmamgain]

May I also ask reviewers for review on https://github.com/TRI-ML/dgp/pull/136 ?

@kuanleetri Since PR authors cannot request reviewers on the PR itself (unless they have Write/Admin privileges), could you please also suggest if there is any existing workflow where PR authors can request for review.

[nehalmamgain]

nehalmamgain requested review from tk-woven and removed request for kuanleetri

I clicked on re-request button for review for tk-woven, and this automatically removed @kuanleetri This does not happen on our other development repos, and probably has to do with the same issue mentioned above.

[nehalmamgain]

Thanks Tyler! The schema has been merged previously. This PR is more so for plumbing and follows the structure of other objects existing on the repo.

@kuanleetri I would like to merge this by EOD (with comments address ofc) to unblock my experimentation. If any changes are needed later, I would be happy to address them in another PR.

[nehalmamgain]

Thank you kindly! 🙇‍♀️