feat: Update to OPA v1.2.0 (#373)

Regorus now defaults to rego v1. `import rego.v1` is no longer needed.
Additionally, `future` keywords are automatically imported.

See
https://www.openpolicyagent.org/docs/latest/v0-upgrade/#changes-to-rego-in-opa-v10
to understand the differences between rego v1 and v0.

BREAKING CHANGE:

v0 style policies will error out by default. To enable v0 behavior, call engine.set_rego_v0(true) before
loading policies.

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

bindings/ruby/ext/regorusrb/src/lib.rs

@@ -36,6 +36,11 @@ impl Engine {
         }
     }
 
+    fn set_rego_v0(&self, enable: bool) -> Result<(), Error> {
+        self.engine.borrow_mut().set_rego_v0(enable);
+        Ok(())
+    }
+
     fn add_policy(&self, path: String, rego: String) -> Result<String, Error> {
         self.engine
             .borrow_mut()
@@ -297,6 +302,9 @@ fn init(ruby: &Ruby) -> Result<(), Error> {
     // defines <, <=, >, >=, and == based on <=>
     engine_class.include_module(module::comparable())?;
 
+    // rego language configuration
+    engine_class.define_method("set_rego_v0", method!(Engine::set_rego_v0, 1))?;
+
     // policy operations
     engine_class.define_method("add_policy", method!(Engine::add_policy, 2))?;
     engine_class.define_method(