Remove SourceTerm superclass

[EmilyBourne]

Remove the SourceTerm superclass. There are many types of SourceTerm. Managing this via a std::variant in the ConfigParser causes the linker to overuse resources (this lead to freezes on my local laptop). To avoid this problem a solve method is added to the ConfigParser which calls GMGPolar.solve with local instances of the necessary boundary conditions and source term. Closes #131

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[codecov]

Codecov Report

❌ Patch coverage is 5.00000% with 285 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.69%. Comparing base (6787376) to head (8a36f8b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ConfigParser/select_test_case.cpp	5.00%	285 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #209      +/-   ##
==========================================
- Coverage   95.32%   90.69%   -4.64%     
==========================================
  Files          86       86              
  Lines        9372     9433      +61     
==========================================
- Hits         8934     8555     -379     
- Misses        438      878     +440     

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[julianlitz]

My laptop froze as well if compiled with multiple threads because it ran out of the 8GB memory. @EmilyBourne Would be nice if that can be improved.

[julianlitz]

Over the last few weeks I probably had like 20 freezes with VS Code taking up to 10 minutes to finally crash 😂

[EmilyBourne]

My laptop froze as well if compiled with multiple threads because it ran out of the 8GB memory. @EmilyBourne Would be nice if that can be improved.

😆 This is always a danger with templating. I don't think we instantiate any more instances of the classes than you did before though so I'm not sure why this is so bad for you. Maybe try compiling with less parallelism?

[julianlitz]

With 2 VS instances running, only one threaded compilation works and with a single VS Code instance I can use 2 threads (before your new PR. Maybe now its better)