Migration tooling

[workingjubilee]

We should be able to automatically revise postgrestd to handle new releases. This mostly means we need to rewrite a very small amount of what is in the std::sys module. We can do this through git (ideal) or via more fiendish means (maybe tragically necessary).

I expect I will do about one or two more migrations manually because it was not clear to me at the time what the automation tooling should be doing.