jinja : reduce template rendering overhead (#32023)
* jinja : reduce value allocation and lookup overhead
Assisted-by: GPT-6 Astra
* jinja : address rendering review feedback
Assisted-by: GPT-6 Astra
* jinja : test multipart strings and simplify lookup
Assisted-by: GPT-6 Astra
* fix "undefined hint"
* fix divisibleby 0
* clean up
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Co-authored-by: Xuan Son Nguyen <son@huggingface.co>
