Fix for a bug in the compilation of controlled gates

[gadial]

Summary

Fixes a bug in the compilation of controlled gates resulting in X gates added in incorrect positions.

Fixes #2252

Details and comments

When adding a gate with control qubits, a control state string determines whether the control qubit should be 1 or 0. In the case of 0, compilation adds an X gate before and after the application of a standard, controlled-by-1 gate. The code for adding the X gates is

for i in range(len(qubits)):
   if (ctrl_state >> i) & 1 == 0:
     qubits_i = [qubits[len(qubits) - 1 - i]]
     aer_circ.gate("x", qubits_i, params, [], conditional_reg, aer_cond_expr, label if label else "x")

The code goes over the qubit list in reverse order, which does not correspond to the way the control string is interpreted in Qiskit, and the loop goes over all the qubits in the gate, including the target qubit, resulting in X gates always added before and after this qubit (creating a non-equivalent behavior if, e.g. the controlled gate is Z).

This PR addresses this issue by going over the qubits in the standard order and not handling the last one in the qubits list.