Add support for URI format in JSON schema validation

[Muhtasham]

This PR adds support for the URI format in JSON schema validation. Previously, attempting to use the "uri" format in a schema would raise a NotImplementedError especially when serving with vLLM.

This change implements regex support for URI validation, allowing users to specify URI fields in their guided JSON requests.

[rlouf]

Awesome, and good idea to refactor this! Would you mind adding a couple of tests?

[RobinPicard]

Hi @Muhtasham! We recently released Outlines v1. Turning a json schema into a regex is now handled in outlines-core. As the URI format is already supported there, I'm going to close the PR.