Allow more generic hessian set types

[gdalle]

This PR is not done yet

Source

• Add two variants of connectivity_tracer_i_to_j, gradient_tracer_i_to_j and hessian_tracer_i_to_j: one for AbstractTracer and one for AbstractSet
• Use gradient_tracer_i_to_j inside hessian_tracer_i_to_j for separation of concerns
• Allow more generic eltype in the various custom sets, so that they can hold Tuple{Int,Int}
• Start implementing clever union! and product, but we will need the more sophisticated union_product! I introduced for Hessians

Tests

• Add some tests for cartesian products
• Start adding tests for Hessian tracers with H != Set{Tuple{Int,Int}}

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.86486% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 84.19%. Comparing base (59ae75c) to head (2b64b8c).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/settypes/recursiveset.jl	33.33%	8 Missing ⚠️
src/overload_connectivity.jl	87.50%	3 Missing ⚠️
src/settypes/duplicatevector.jl	80.00%	2 Missing ⚠️
src/overload_hessian.jl	97.22%	1 Missing ⚠️
src/tracers.jl	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #103      +/-   ##
==========================================
- Coverage   84.56%   84.19%   -0.37%     
==========================================
  Files          18       18              
  Lines         758      829      +71     
==========================================
+ Hits          641      698      +57     
- Misses        117      131      +14     

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[gdalle]

@adrhill can you take a look and validate the general direction?

[adrhill]

The new overloads are exactly what I imagined. 👍

[gdalle]

The benchmark failures are caused by UInt64, please merge #109 first

[adrhill]

#109 has been merged.

[adrhill]

Internal representations for Gradient and Hessian information should be decoupled and abstracted away. The only interface between the two should be union_product!.

This requires

• removing type restrictions in overload_hessian.jl (see here)
• adding tests on different Gradient and Hessian set types (see here)
• most likely implementing more methods for union_product!