Add test cases for return slot allocation.

test/libyul/evmCodeTransform/stackReuse/function_retparam_for.yul

@@ -0,0 +1,27 @@
+{
+    function f() -> x { pop(address()) for { pop(callvalue()) } 0 {} { } }
+}
+// ====
+// stackOptimization: true
+// ----
+// PUSH1 0x19
+// JUMP
+// JUMPDEST
+// PUSH1 0x0
+// ADDRESS
+// POP
+// CALLVALUE
+// POP
+// JUMPDEST
+// PUSH1 0x0
+// ISZERO
+// PUSH1 0x15
+// JUMPI
+// JUMPDEST
+// PUSH1 0xA
+// JUMP
+// JUMPDEST
+// JUMPDEST
+// SWAP1
+// JUMP
+// JUMPDEST