WIP: Introduce defineModule function to declare a module before registering

[mickmister]

In order to make the initialization process more explicit, and facilitate dependency injection more easily, we are pivoting to explicit registering of modules instead of implicit registering through side effect imports.

[mickmister]

We should then be able to do the following, even though it wouldn't make sense for a Main module:

declare module 'springboard' {
    interface DefinedModules {
        Main: typeof mod;
    }
}