Switch tests and documentation to use qiskit-ibm-runtime fake backends

[wshanks]

The IBM-specific fake backends in Qiskit are being removed in Qiskit 1.0 in Qiskit/qiskit#11376. The same fake backends have been moved to qiskit-ibm-runtime in
Qiskit/qiskit-ibm-runtime#1140 and follow up PRs.

Here the qiskit imports are replaced with qiskit-ibm-runtime imports in order to provide a smooth transition between Qiskit 0.45 and Qiskit 1.0. In the future, it may be preferable to use generic fake backends maintained in the repo and not depend on qiskit-ibm-runtime for them.

Additionally, this commit reorders the requirements-dev.txt file so it
is easier to read and adds qiskit-ibm-runtime as a development
dependency. It also temporarily pins qiskit to 0.45 while other
deprecations are addressed.

[wshanks]

Note: this PR is marked as a draft because it requires currently unreleased qiskit-ibm-runtime code as noted in Qiskit/qiskit-ibm-runtime#1317.

[wshanks]

This PR will allow qiskit-experiments tests to keep working against Qiskit 0.45 and main when the fake backends are removed from main. In the future when Qiskit 1.0 is released, I think we might want to switch to using internal test backends that we generate using Qiskit/qiskit#10266 because Qiskit 1.0+ will be more stable than qiskit-ibm-runtime and there would be less chance of updates breaking the tests.

[wshanks]

qiskit-ibm-runtime 0.18.0 has been released, so this change is usable now. However, currently, we uninstall qiskit-ibm-provider in our tests to run against Qiskit main and the code we are trying to avoid in qiskit-ibm-provider is moving to qiskit-ibm-runtime (see my comment here: Qiskit/qiskit-ibm-runtime#1285 (comment)). If we make qiskit-ibm-runtime a hard test requirement here, we won't be able to do the uninstall trick to avoid it. We could just pin qiskit-ibm-runtime temporarily if that happens, or install it from a patched git branch in the Qiskit main test environment.

[wshanks]

Rebased on #1375 which should be merged first (unrelated fix to unblock CI).

[coruscating]

This needs to be merged to make CI work again now that 0.46 has been released with a deprecation warning when using fake backends.

[wshanks]

We have to keep an eye on the qiskit-ibm-runtime releases. On the main branch of qiskit-ibm-runtime, the qiskit-ibm-provider code has been merged in including the code incompatible with Qiskit 1.0 that makes us uninstall qiskit-ibm-provider in our Qiskit main tox environment. Probably Qiskit/qiskit-ibm-runtime#1365 will get merged before the next release and it will be compatible with Qiskit 1.0. If there is some other issue though, we won't be able to do the removal trick.

[wshanks]

Oops, I removed all the place name backends but I didn't realize that FakeBackendV2 was also deprecated in Qiskit.

[wshanks]

We probably also need #1384? I didn't test my recent change locally.

[coruscating]

Ah, you're right. Do you want to rebase the changes in #1384 to this PR? They looked fine.

[wshanks]

I pinned qiskit here and then we can unpin it in #1384.

[wshanks]

Hmm, my first pin didn't work...it annoys me how tox hides the output of pip explaining why it is installing what it is installing. I am not sure why qiskit 0.46 still got installed with my first attempt.