Adds metadata reading of Siemens Raw Pet Data types

[tclose]

Adds metadata reading of Siemens Raw Pet Data types, which have a DICOM header embedded in them at the end of the file

[codecov]

Codecov Report

Attention: Patch coverage is 71.18644% with 17 lines in your changes missing coverage. Please review.

Project coverage is 84.98%. Comparing base (5648b7f) to head (c381b0e).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
extras/fileformats/extras/medimage/raw.py	53.84%	6 Missing ⚠️
fileformats/medimage/raw/pet/siemens.py	66.66%	6 Missing ⚠️
extras/fileformats/extras/medimage/nifti.py	25.00%	3 Missing ⚠️
fileformats/medimage/base.py	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #32      +/-   ##
==========================================
- Coverage   86.28%   84.98%   -1.30%     
==========================================
  Files          30       31       +1     
  Lines         707      746      +39     
==========================================
+ Hits          610      634      +24     
- Misses         97      112      +15     

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