[BUG] qml.transforms.to_zx not properly translating adjoint ops

[Qottmann]

The main culprit is that pyzx is working with exact fractions whereas pennylane works with float numbers.
In many cases, a proper translation in qml.transforms.to_zx is provided, but some are missing and causing problems.

adjoint ops are not properly translated

def qfunc():
    qml.T(0)
    qml.adjoint(qml.T(0))

import pyzx as zx

g = qml.transforms.to_zx(qfunc)()
zx.draw(g)

We see the first bare T gate is properly translated to a Z_pi/4 spider, but its adjoint is not.
This makes retrieving the PL circuit impossible:

>>> qml.transforms.from_zx(g)
(..)
AttributeError: 'float' object has no attribute 'denominator'

This is a problem because decompositions of e.g. Toffoli gates contain adjoint T and S gates.