Combination of symbolic and not symbolic parameters

[SamDuffield]

Currently, this functionality is not supported but is desirable

e.g. a circuit of the form

from sympy import Symbol
from pytket.circuit import Circuit

symbols = [Symbol("p0")]
circuit = Circuit(1)
circuit.Rz(symbols[0], 0)
circuit.Rz(0.1, 0)

Ideally, this should understand that the second Rz gate should be unparameterised

[SamDuffield]

Functionality added in 0.6.0 #47