Use `add_lease` instead of `renew_lease`

Previously Hypothesis spent a long while putting storage indexes on the
storage servers and creating a list of nodes with non-overlapping storage
indexes and then asserting that, out of no relevant shares, none had expired
leases.

Now all storage servers in the test will have all of the relevant shares and
so all should be visited and updated.

Switch to fully using the 31 day lease time

Increase PaymentController RETRY_INTERVAL to 1 sec

Rename the slot-related strategies

Make DummyRedeemer require a public key

We're going to start looking at it.  It's not reasonable for its value to be None.

Disregard element order when checking invalid pass information

The order of the passes only comes from Python dictionary iteration order.  It is largely meaningless.

Add a `__str__` to MorePassesRequired

Set up Cachix cache to speed up builds (beyond even the point where CircleCI stops timing them out)

Co-authored-by: Tom Prince <tom.prince@hocat.ca>

We collect coverage info so we can't very easily run on multiple cores.  So we
mostly can't take advantage of the bigger machine.

With Cachix we can now cache even partial build successes so even if we lose
the whole cache and have to start from scratch, the build should now converge
on success even if it takes a few tries.

hope it does not break the build cachix setup step

Attempt to set up a scheduled NixOS job workflow to refresh the CircleCI cache

Also move this time to a point shortly in my future so it will run and I can
see what happens.

Account for leading and trailing whitespace around the Ristretto key when reading it from a file