Split ExternalFileScanNode into FileQueryScanNode and FileLoadScanNode. Remove some useless code in FileLoadScanNode. Remove unused config item: enable_vectorized_load and enable_new_load_scan_node
Split ExternalFileScanNode into FileQueryScanNode and FileLoadScanNode. Remove some useless code in FileLoadScanNode. Remove unused config item: enable_vectorized_load and enable_new_load_scan_node