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/java/src/lib.rs

@@ -28,6 +28,20 @@ pub extern "system" fn Java_com_microsoft_regorus_Engine_nativeClone(
     Box::into_raw(Box::new(c)) as jlong
 }
 
+#[no_mangle]
+pub extern "system" fn Java_com_microsoft_regorus_Engine_nativeSetRegoV0(
+    env: JNIEnv,
+    _class: JClass,
+    engine_ptr: jlong,
+    enable: bool,
+) {
+    let _ = throw_err(env, |_env| {
+        let engine = unsafe { &mut *(engine_ptr as *mut Engine) };
+        engine.set_rego_v0(enable);
+        Ok(())
+    });
+}
+
 #[no_mangle]
 pub extern "system" fn Java_com_microsoft_regorus_Engine_nativeAddPolicy(
     env: JNIEnv,