Fix normalization of image id for singularity pre-pulled images

[spinto]

Apptainer will replace the ':' character with an '_' when the image is pulled during pre-pull, not a '/'.

In fact, '_latest' is correctly added if a ':' is not present. I am not sure what is the reason for the '/' replacement, as '/' is not allowed at all in the docker image name+tag.

This pull fixes the replacement of the ':' character.

[mr-c]

What does singularity do in recent versions? If it is something different, then we'll need an apptainer specific fix

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.61%. Comparing base (72051e2) to head (6d553ee).

Files with missing lines	Patch %	Lines
cwltool/singularity.py	0.00%	2 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (72051e2) and HEAD (6d553ee). Click for more details.

HEAD has 6 uploads less than BASE

Flag	BASE (72051e2)	HEAD (6d553ee)
	18	12

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2171      +/-   ##
==========================================
- Coverage   85.18%   77.61%   -7.58%     
==========================================
  Files          46       46              
  Lines        8332     8332              
  Branches     1954     1954              
==========================================
- Hits         7098     6467     -631     
- Misses        768     1346     +578     
- Partials      466      519      +53     

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[spinto]

@mr-c I have just tested with the latest SingularityCE, and it also replaces the ':' with '_'

[mr-c]

Okay, now we need to figure out which versions of singularity & apptainer have which behavior