OPA Conformance

- Disable default features of jsonschema to reduce binary size (#85)
- graph.reachable, graph.reachable_paths builtins.
- In progress walk builtin
Note: graph.reachable_paths is buggy in upstream OPA and its semantics
  are not well defined.
  https://github.com/open-policy-agent/opa/issues/5871
  https://github.com/open-policy-agent/opa/issues/6128
- Use correct feature for regex
- Ensure that regorus complies with all features disabled.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/utils.rs

@@ -133,6 +133,8 @@ fn get_extra_arg_impl(
                 } else {
                     return Ok(None);
                 }
+                #[cfg(not(feature = "deprecated"))]
+                return Ok(None);
             }
         };
         if (n_args as usize) + 1 == params.len() {