lang: funcs: facts: Add CallableFunc implementation for fact

Add an initial implementation for this wrapper function.

lang/funcs/facts/func.go

@@ -79,3 +79,13 @@ func (obj *FactFunc) Init(init *interfaces.Init) error {
 func (obj *FactFunc) Stream(ctx context.Context) error {
 	return obj.Fact.Stream(ctx)
 }
+
+// Call means this function implements the CallableFunc interface and can be
+// called statically if we want to do it speculatively or from a resource.
+func (obj *FactFunc) Call(args []types.Value) (types.Value, error) {
+	if i, j := len(args), 0; i != j {
+		return nil, fmt.Errorf("arg length doesn't match, got %d, exp: %d", i, j)
+	}
+
+	return obj.Fact.Call()
+}