Remove psutil as a dependency

[FabianBrings]

Summary

Removes any uses of psutil and the corresponding dependency

Details and comments

As described in issue #11254, psutil is used to detect the number of cores and memory to optimize resource allocation. The actual usefulness of those information is however questionable, while adding additional bloat. Therefore any references to the module were modified, the unit tests fixed and the dependencey removed.

[qiskit-bot]

Thank you for opening a new pull request.

Before your PR can be merged it will first need to pass continuous integration tests and be reviewed. Sometimes the review process can be slow, so please be patient.

While you're waiting, please feel free to review other open PRs. While only a subset of people are authorized to approve pull requests for merging, everyone is encouraged to review open pull requests. Doing reviews helps reduce the burden on the core team and helps make the project's code better for everyone.

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[CLAassistant]

All committers have signed the CLA.

[FabianBrings]

The code test fails, because qiskit-aer uses the memory information from psutils, which is being obtained in qiskit. This was changed 2 days ago, so qiskit-aer now obtains the information on its own by using psutil. Does anything about the test need to be changed or will it eventually use the newer version? Best reagards, FB.

[jakelishman]

When Aer 0.13.1 releases some time next week, that will no longer need Qiskit to depend on psutil, so we'll be able to move to merge around then. In the mean time, we'll need to get the CLA bot sorted out - your commits are made with two different email addresses, and one of the emails is registered to a different GitHub account. Either you'll need to log in with that account to also sign the CLA, or you'll need to rebase the commits and modify the author/email in them to be the ones associated with this GitHub account.

[jakelishman]

Your branch has gone a bit wrong here, and can't be fixed just by merge commits. You'll need to rebase your changes to discard the unintended commits, though if you're not sure how to do that, you might find it easier to reproduce your change onto a clean checkout of the repository. Typically it's easier to make PRs from a new branch in your fork rather than your main branch - you can see some instructions on the process we suggest in the GitHub documentation.