Allow to configure gate set for E-VQE

[svenpruefer]

We may extend the gate set among which E-VQE chooses randomly to include all gates available in Qiskit, or in particular those from real hardware devices.

In particular, IBM currently supports the following gates:
Heron R2: CZ, ID, RZ, SX, X
Heron R1: CZ, ID, RZ, SX, X
Eagle R3: ECR, ID, RZ, SX, X

Among these, all are single-qubit, except for CZ and ECR.