Package selector dialog

[cohaereo]

See for reference: https://github.com/cohaereo/alkahest/blob/main/crates/alkahest/src/game_selector.rs

It will need a bit of an upgrade for Quicktag

1. Preferably hosted in the main quicktag window
2. Defer initializing the packagemanager and main application until after we select a package
3. Add a version/platform dropdown to the selector
4. Read existing version/platform paths from package path cache