Remove MarginalLogDensitiesExt

[ArpanC6]

What

Eliminate the DynamicPPLMarginalLogDensitiesExt extension completely from DynamicPPL.jl.

Why

The initial intention behind adding the extension to DynamicPPL was that DynamicPPL.marginalize would be overloaded when MarginalLogDensities.jl was loaded. As per the discussion in ElOceanografo/MarginalLogDensities.jl#47, the plan now is to make it part of the functionality of MarginalLogDensities.jl and hence it should not exist as an extension anymore.

Changes

• Delete ext/DynamicPPLMarginalLogDensitiesExt.jl and its test file
• Remove MarginalLogDensities from [weakdeps], [extensions], and [compat] in Project.toml and test/Project.toml
• Remove marginalize function definition and its associated `register_error

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.17%. Comparing base (8f52e83) to head (5af3d36).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1392      +/-   ##
==========================================
+ Coverage   78.56%   82.17%   +3.61%     
==========================================
  Files          50       49       -1     
  Lines        3522     3518       -4     
==========================================
+ Hits         2767     2891     +124     
+ Misses        755      627     -128     

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