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>

tests/coverage/mod.rs

@@ -45,6 +45,7 @@ fn yaml_test_impl(file: &str) -> Result<()> {
 
         let mut engine = Engine::new();
         engine.set_enable_coverage(true);
+        engine.set_rego_v0(true);
 
         for (idx, rego) in case.modules.iter().enumerate() {
             engine.add_policy(format!("rego_{idx}"), rego.clone())?;