Put all the convert.py hooks into __init__.py?

[quantshah]

I was trying to find out where the initial hooking of qutip-tensorflow and qutip happens and it turns out that its all done in convert.py when imported in the the init.py. I feel it would be a bit more verbose to see this happen inside the init as qutip-cupy does it. That makes it very clear to see and follow the magic of how qutip-tensorflow hooks on to the data layer.

@AGaliciaMartinez what do you think? I will follow this for qutip-jax.

[AGaliciaMartinez]

That sounds good! I will update it to be consistent with the other packages. thanks for letting me know!