Reduce fs client mem usage by not loading pixels into dicom_datasets

Query/retrieve services don't return pixel data, and all fetch operations in the filesystem client copy the full files that include the pixel data.

pacsman/filesystem_dev_client.py

@@ -55,7 +55,7 @@ def __init__(self, dicom_dir: str, dicom_source_dir: str, *args, **kwargs) -> No
 
     def _read_and_add_data_set(self, filename: str) -> None:
         filepath = self._filepath(filename)
-        self._add_dataset(dcmread(filepath), filepath)
+        self._add_dataset(dcmread(filepath, stop_before_pixels=True), filepath)
 
     def _add_dataset(self, dataset: Dataset, filepath: str = None) -> None:
         if filepath is None: