Create an integrated state object
This creates a new lava-api-mock crate, which is built from new crates made during its construction process:
- persian-rug for linking things together.
- boulder for creating instances.
- clone-replace for a mutable store without lifetimes on its guards.
- django-query for mocking the Django API of lava
There are minor changes to the lava-api itself, including the addition of tests.
This MR currently supercedes !12 (closed) (it contains the same code as a part of it).