(TypeScript) Enforce source order

[mcmire]

To make files look the same, we should enforce the following order:

1. Types
2. Enums
3. Constants
4. Functions

In test files, the order should look like this:

1. Module mocks (using jest.mock)
2. Typed module mocks (using jest.mocked)
3. Types
4. Enums
5. Constants
6. Tests
7. Functions

In some cases, a file may be so long that the author may wish to locate a type next to the place in which it's used, such as options for a function. Instead of doing this, this should act as a code smell and should indicate that we ought to move the function along with its type to a separate file.