Function broot::verb::internal_focus::on_internal

pub fn on_internal(
    internal_exec: &InternalExecution, 
    input_invocation: Option<&VerbInvocation>, 
    trigger_type: TriggerType, 
    selected_path: &Path, 
    screen: Screen, 
    con: &AppContext, 
    tree_options: TreeOptions
) -> CmdResult

general implementation for verbs based on the :focus internal with optionally a bang or an argument.