JsonSchema does not define format=url, as requested by host parameters validation

https://github.com/Azure/azure-openapi-validator/blob/main/docs/host-parameters-validation.md specifies:
```If a parameter matches belows, therefore it must be called 'endpoint' and be typed 'type:string, format:url'```

However, `url` is not a defined format in [JsonSchema](https://json-schema.org/understanding-json-schema/reference/string.html#built-in-formats). A [previous request](https://github.com/json-schema-org/json-schema-spec/issues/233) to add "url" as a JsonSchema format was rejected. Should we recommend users specify `uri` as format instead?

@mikekistler