Notably:
- Cleaned up/refined checksum handling
- Updating checksums now doesn't force remove already installed dependencies (deps are now always downloaded in a separate temporarily directory when updating checksums)
- Sources are now automatically backed up and restored upon download errors (if already installed)
- We no longer try to perform post-actions if necessary (ex. when the user cancels the download or if checksum validation fails)
- Minor formatting
Signed-off-by: celenity <celenity@celenity.dev>