Added stats collection in pytket script

from pytket.pauli import Pauli

from pytket.extensions.qiskit import AerStateBackend

from pytket.passes import FullPeepholeOptimise

from statistics import mean, stdev

nb_steps = 100

step_size = 0.01

n_qubits = [5, 10, 20, 30, 40, 50]

n_runs = 10

for nb_qubits in n_qubits:

  data = []

  for run_id in range(n_runs):  

    # Start timer

    start = time.time()

    circ = Circuit(nb_qubits)

    FullPeepholeOptimise().apply(circ)

    end = time.time()

  print('n_qubits =', nb_qubits, '; Elapsed time =', end - start, '[secs]')

    data.append(end - start)

  print('n_qubits =', nb_qubits, '; Elapsed time =', mean(data), '+/-', stdev(data),  '[secs]')

    # for com in circ: # equivalently, circ.get_commands()

    #   print(com.op, com.op.type, com.args)

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