bundle: refactor remaining bundle extensions

- Move the remaining non-`brew`/`cask`/`tap` bundle types onto the single-file extension path so `mas`, `vscode`, `cargo`, and `flatpak` keep their DSL, dump, check, install, and cleanup behavior in one place while shared bundle callers infer flags and selection from the registered extensions.
- Keep the existing checker, dumper, and installer entrypoint files as compatibility requires and preserve the current check, dump, and cleanup ordering so the existing bundle specs continue to exercise the same public constants and command behavior.