common : add --override-tensor-draft, --cpu-moe-draft and --n-cpu-moe-draft parameters (#15191)

* Checkpoint from VS Code for coding agent session

* Initial plan

* Fix typo in --override-tensor-draft flag implementation

* Add null termination for speculative tensor buffer overrides

* Apply suggestions from code review

* Apply suggestions from code review

* Extract tensor override parsing logic to common function (addresses @slaren's feedback)

* Apply suggestions from code review

* Apply suggestions

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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Diego Devesa <slarengh@gmail.com>