llama-bench: add `-d` depth arg (#13096)
* add depth param
* update llama-bench README and add depth param
* llama-bench: default params for depth arg for faster execution
* Update examples/llama-bench/README.md
Co-authored-by: Johannes Gäßler <johannesg@5d6.de>
* fix buffer print ub
* use user provided args
* remove extra whitespaces
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Co-authored-by: Johannes Gäßler <johannesg@5d6.de>