Test pre-release notebooks after pre-release in isolation
Description of the issue
Our notebook test infra is pretty good but has one gap: pre-release notebooks are not tested in isolation, only on PRs against the given branch. This gap should be covered by a test that runs after a master commit triggered the pre-release to pypi, the new release is in the index and should cover all the notebooks that have pre-release cirq installed in them.
Do we know if this was already done? Otherwise it seems simple enough to add, but not priority for 1.0.
Discussed with Pavol: this could be added as a CI job for checking PRs. Main thing is that it would have to get Cirq from pypi, not from sources.
This will exercise the notebooks that users would get.