Preserving the order of the keys in json-schema-to-grammar by using nlohmann::ordered_json

[mgonzs13]

Prerequisites

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Feature Description

Using ordered JSONs in json-schema-to-grammar so that the llama.cpp follows the order of the JSON schema.

Motivation

I've been trying the new C++ json-schema-to-grammar from #5978 and I've noticed that there is no prop_order, which is present in the python version, to order the keys of the JSON schema. I think this could be interesting since generating text for some specific keys can improve the text generation of the following keys.

Possible Implementation

An easy solution is replacing the base json nlohmann::jsonwith nlohmann::ordered_json in both files json-schema-to-grammar.h and json-schema-to-grammar.cpp. This will result in JSON that preserves the original order of the keys.

[mgonzs13]

Solved in #6232