Remove limitation that requires Subject Context to be present in SRs

[CPBridge]

The TID1001 Subject Context template within TID1500 SRs is optional and only needs to be provided if the information is not inherited from the source images. Slim requires it in order to match SRs to source images. Without it the SR annotations do not appear at all within slim.

https://dicom.nema.org/medical/dicom/current/output/chtml/part16/chapter_A.html#sect_TID_1009

We should loosen this restriction to allow slim to match images that reference the correct images.

I have prepared some test data for this. Here is the same SR with and without the subject context specimen information:

• gs://idc-annotation-conversion-outputs/2023-12-01_rms_sr_tests/PAIZZZ-0ATDI7_sr.dcm
• gs://idc-annotation-conversion-outputs/2023_12_07_rms_sr_without_subject_context/PAIZZZ-0ATDI7_sr.dcm

These annotations refer publicly available images in the IDC collections and can be downloaded from:

• gs://public-datasets-idc/73b6b17f-ddab-4baa-a233-2e8cf70c54a0/480f84f2-ba3e-4d69-9ae8-570b42211cbd.dcm
• gs://public-dataset-idc/73b6b17f-ddab-4baa-a233-2e8cf70c54a0/fd3d0ae5-3d60-4d84-8e47-9edf77b7af20.dcm

@dclunie @fedorov