Adjustments to work with SteamKit CDNClient refactor.
Use uints for app and depot Ids to require less casts for SteamKit.
Removed old Steam2 beta option.
Simplify arg handling.
Allow downloading of specified manifest.
Fixed exception when not using -dir and build id unknown.
Removed unused function.
Save manifests to optimize needed chunks check. Add -validate option. Concurrent donwloads.
Try other servers if failing to get manifest from one.
Remove no-long-used AppInfoOverridesCDR var.
Use console instance when possible. (now caches user sentry data and steam id to config.vdf).