Sys bio model fixes

[CodeByDrescher]

Fixes more problems found in Sys-bio models, including:

• Using MathML style references to biological concepts when performing ModelAttributeChanges

[codecov]

Codecov Report

Attention: Patch coverage is 90.62500% with 6 lines in your changes missing coverage. Please review.

Project coverage is 88.81%. Comparing base (8218c5b) to head (0f5be30).
Report is 10 commits behind head on dev.

Files with missing lines	Patch %	Lines
biosimulators_utils/sedml/utils.py	89.83%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #154      +/-   ##
==========================================
- Coverage   88.83%   88.81%   -0.02%     
==========================================
  Files          89       89              
  Lines        9635     9668      +33     
==========================================
+ Hits         8559     8587      +28     
- Misses       1076     1081       +5     

Flag	Coverage Δ
unittests	88.81% <90.62%> (-0.02%)	⬇️

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[sonarcloud]

Quality Gate failed

Failed conditions
7 Security Hotspots

See analysis details on SonarCloud