model : add Jina Embeddings v5 Nano (partial EuroBERT) support (#19826)

model : add Jina Embeddings v5 Nano (partial EuroBERT) support (#19826)

* WIP: Add EuroBERT support with autoformatting changes

This commit includes:
- EuroBERT model implementation for GGUF conversion
- C++ backend support for EuroBERT architecture
- Unintended autoformatting changes to Python files

Saving before reverting formatting-only changes.

* feat: add back eos assert when not last token pooling

* feat: removed duplicated code and cleanup

* feat: removed not working architectures and unnecessary check

* fix: typo

* fix: dynamic pooling config

* feat: added an example model for eurobert

* feat: proper llama-vocab implementation for jina-v5

* fix: removed unnecessary comments