[Model] Qwen3.5 dense and MoE support (no vision) (#19435)

• Unified delta net handling

• Remove old methods.

• Refactor and optimize

• Adapt autoregressive version from @ymcki

• Change to decay mask approach

• Fix bad permute

• Qwen 3.5 support

• Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret sigbjorn.skjaeret@scala.com

• Further fixes

• Use inheritance, remove unneeded conts

• Not like this!

• Remove ggml.h explicit import

• Remove transformers, fix the views

• ACTUALLY fix views, make super calls explicit in conversion.