Organise clients module packages

[patchwork01]

The clients module has a "util" package that contains a lot of code that doesn't seem related to each other. We could break out a lot of these parts into their own packages.

The root package in the module contains a number of query clients which could sit in their own package.

The package sleeper.clients.status.update doesn't seem related to the "status" package it sits under, and could be moved elsewhere or broken up.

All the scripts that call into these clients will need to be updated if we move the classes around.

We can make sure we move the tests to match how we move the production code.