Extract tests from source directory.

Ensure warnings have been accounted for.

Implement and fix list functions and their tests.

Use modes for list teardown calls to prevent pollution of the tracked
calls.

Use node pointers instead of duplicating the find function logic.

Add context on all log items.

Put mocks to directory structure mimicking project structure.

Use abstraction instead of using SDL dependencies.

Come up with our own logging system.

Instead of using macros, use iterators built-in on each list for
filtering and traversing.

Add some missing parts.

Remove symlinks and make codebase use common modules instead.

Ensure mounts are configurable.

Split callback logic into several functions.

Update initialization method.

Allow current item pointer to have custom type.

Change the pool list initializations.

Add memory and data-related implementations for handling game data.

Properly mock video function dependencies.

Correctly dereference pointers.

Update input tests.

Declare memory before processing.

Declare variables early on.

Add geometry methods for point, vector, and rectangle.