- Default to interactive mode and remove the `--interactive` flag
- Use `--force` to skip interactivity
- Change MSVC dependency storage organization on disk: put each version
  into its own folder and directly refer to the versioned folders,
  providing immutability and making the installation list redundant
- Reuse `host_triple()` function to fix broken bootstrapper dispatching
- Simplify code:
  - Remove or inline many unused and redudant functions and variables
  - Prefer plain functions to classes
  - Consolidate into fewer files, remove unnecessary bootstrapper/ dir
- Improve Python style
- Sort dependency list