Function find_missing_epochs_dirs

pub async fn find_missing_epochs_dirs(
    store: &Arc<DynObjectStore>,
    success_marker: &str,
) -> Result<Vec<u64>>

This function will find missing epoch directories in the input store and return a list of such epoch numbers. If the highest epoch directory in the store is epoch_N then it is expected that the store will have all epoch directories from epoch_0 to epoch_N. Additionally, any epoch directory should have the passed in marker file present or else that epoch number is already considered as missing. The returned list will contain epoch_N+1.