feature: keep config persistent after reset or restart if the stream is unavailable during restart

[YehorFedorov]

Once I added the restart_streams API I found that manager::start_default function has the next line

    // Gently remove all streams as we are going to replace the entire list below
    remove_all_streams().await?;

Which was removing the full configuration. After a restart, the config contains the streams that were available during the restart and other disappeared

remove_all_streams is only called from start_default, so I decided to resolve this simply by providing a flag, that allow or prevent the config file from modification

What do you think?