Fix: propagate interpolate_pos_encoding through PixioEmbeddings and PixioModel

[aashirpersonal]

Summary

This PR fixes #44716 by exposing and forwarding interpolate_pos_encoding through the Pixio embedding/model call chain so the option is actually usable from PixioModel.forward().

Changes

• Added interpolate_pos_encoding: bool = False to PixioEmbeddings.forward() and forwarded it to self.patch_embeddings(...).
• Added interpolate_pos_encoding: bool = False to PixioModel.forward() and forwarded it to self.embeddings(...).
• Kept behavior and defaults aligned with similar vision models (e.g. SigLIP patterns) by defaulting to False.

Why

PixioPatchEmbeddings.forward() already accepted interpolate_pos_encoding, but higher-level modules did not pass it through, making the parameter effectively inaccessible for end users.

Issue: #44716

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: pixio

[Rocketknight1]

No drive-by code agent PRs, please! We block people who do this repeatedly.