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/csharp/net8.0/Program.cs

@@ -23,6 +23,7 @@ var w = new Stopwatch();
 w.Restart();
 
 var engine = new Regorus.Engine();
+engine.SetRegoV0(true);
 
 w.Stop();
 var newEngineTicks = w.ElapsedTicks;