[Performance]: JSONLogitsProcessor repeats the same build_regex_from_schema again and again

[stas00]

Proposal to improve performance

Why does the regex get recompiled on every request? the object gets instantiated for every request and the regex is rebuilt even though most of the time the schema is likely to remain the same.

vllm/vllm/model_executor/guided_decoding/outlines_logits_processors.py

Line 142 in b1f3e18

regex_string = build_regex_from_schema(schema_str, whitespace_pattern)

probably @lru_cache should do the trick here? does it work on object constructors? or would it be cleaner to add a wrapper around build_regex_from_schema and cache that?

This is otherwise similar to #8308?