Support constrained decoding

[Taka152]

This PR adds constrained decoding feature that user can provide regex or json schema to guide the decoding process. This can enable function calls or further increase response quality.

The API looks like the following code, currently it only accepts regex and json_schema type, though context free grammar could be considered in the future.

# python
params.set_guidance("json_schema", json.dumps(json_schema))

// cpp
params->SetGuidance("json_schema", json_str);

The overhead brought by this feature is about 3-5% latency increase and could further optimized after continuous decoding feature jump forward steps with only one candidate.

[natke]

We will postpone merging this until we resolve the rust dependency