[asl] Fix let binding of tuples

[maranget]

Fix various problems related to tuple bindings.

• [X] Cyclic program order.
• [X] Impossibility to transmit non-determined value from tuple construction to binding.

Two tests that illustrate the fixed problems are also added.

• Cyclic program order:

  
  ASL return-tuple

{

}

func f() => (integer, integer) begin return (1,2); end

func main() => integer begin let (a,b) = f(); let c = a+b; return 0; end

forall 0:main.0.c=3

Before the fix, this test yielded no execution at all, because if the cyclic `po` introduced while evaluating `let (a,b) = f();`.
- Creating tuples with non-resolved arguments:

ASL frozen-tuple-arg

{ x=15; 0:X0=x; }

func main() => integer begin let x = read_register(0);
let (a,b) = (1,UInt(read_memory(x,32))); let c = a+b; return 0; end

forall 0:main.0.c=16

Before the fix, evaluation of `let (a,b) = (1,UInt(read_memory(x,32)));` was failing because the `read_memory` primitive returns a non-resolved value, resulting in a pair whose second argument is a non-resolved value.

[HadrienRenaud]

Sounds good to me, thank you @maranget for this in depth bug finding

[maranget]

Merged, thanks @HadrienRenaud forthe review.