Add ExpandsTo and FlattensTo helper types

[LukeAbby]

Will be used as:

function takesConfig<T>(config: ExpandsTo<T, { foo: { bar: number } }>) { ... }
function takesData<T>(config: FlattensTo<T, { foo: { bar: number } }>) { ... }

In order to enable functions that call foundry.utils.expandObject and foundry.utils.flattenObject.

[esheyw]

Places this will be useful for:

• BaseEffectSource#_configure