dagger lock update [SELECTOR...]

Problem

1. No dedicated subcommand for managing the lockfile.
2. Can't select a specific lockfile entry to update
3. Can't dry-run update to show what would be updated

Solution

1. dagger ws update moves to dagger lock update since there can be multiple lock files per workspace.
2. lock update allows selecting which entries of the lockfile to update
3. lock update --dry-run print entries that would be updated, without updating them