Add the support for tensor network benchmarking

[liweintu]

This PR addresses issue #41 . It is still work-in-progress (WIP), please do not merge it at this moment.

This WIP PR is created to enable us to iteratively address reviews from @alecandido , @stavros11 and @scarrazza . Also, it allows other teammates to contribute to its implementation because we don't have a specific TNet branch in this repo to contribute code to.

[alecandido]

Since it is WIP I made it draft. In Qibo there is no official policy for use of draft PRs, but I believe that a set of sensible guidelines is the following:

1. make a PR as soon as you start working on something (as you did), to make everyone aware of what you're doing
2. keep it draft for as long as you don't have a candidate to merge
3. when you undraft, add some reviewers (but if you need some help feel free to do it even before)

[liweintu]

Since it is WIP I made it draft. In Qibo there is no official policy for use of draft PRs, but I believe that a set of sensible guidelines is the following:

1. make a PR as soon as you start working on something (as you did), to make everyone aware of what you're doing
2. keep it draft for as long as you don't have a candidate to merge
3. when you undraft, add some reviewers (but if you need some help feel free to do it even before)

@alecandido Yup, this makes sense. And adding reviewers like yourself early is helpful so that we can receive early reviews to guide the designing of the code architecture.