cpu : add FLOOR, CEIL, ROUND and TRUNC unary operators (#16083)

cpu : add FLOOR, CEIL, ROUND and TRUNC unary operators (#16083)

* CPU: Add support for FLOOR,CEIL,ROUND and TRUNC unary operators

- Added the operators to unary op enum
- Implemented API functions
- Implemented forward and unary-op logic in CPU backend
- Updated ggml_get_n_tasks
- Updated operators names array and static_assert
- Updated docs and enabled automatic tests

* docs: add documentation for ggml_trunc and ggml_trunc_inplace in ggml.h

* chore: remove trailing whitespace from ggml.h

* Remove unresolved merge markers

* Apply review suggestions: cleanup formatting, enum order and leftover artifacts

* Regenerate ops.md using create_ops_docs.py