Remove the memory scheduler. Add python3.12 to testing
The memory scheduler has serious issues and should not be used. To not break the config, we can just start defaulting users to a sqlite storage that uses a tempfile.
In this change I also took the time to update the CI to unsplit the test setups. They run fast enough now that the split is not worth it. (there's still unit+integration split, just not a v1 and v2 of each). I also am including python3.12 to the mix, as this is the new latest and greatest