lang: core, funcs: Port some functions to CallableFunc API

Some modern features of our function engine and language might require
this new API, so port what we can and figure out the rest later.

lang/funcs/wrapped/wrapped.go

@@ -150,7 +150,7 @@ func (obj *Func) Stream(ctx context.Context) error {
 			if obj.init.Debug {
 				obj.init.Logf("Calling function with: %+v", values)
 			}
-			result, err := obj.Fn.Call(ctx, values) // (Value, error)
+			result, err := obj.Call(ctx, values) // (Value, error)
 			if err != nil {
 				if obj.init.Debug {
 					obj.init.Logf("Function returned error: %+v", err)
@@ -181,3 +181,9 @@ func (obj *Func) Stream(ctx context.Context) error {
 		}
 	}
 }
+
+// Call this function with the input args and return the value if it is possible
+// to do so at this time.
+func (obj *Func) Call(ctx context.Context, args []types.Value) (types.Value, error) {
+	return obj.Fn.Call(ctx, args) // (Value, error)
+}