Improvements for Trace Computation

[TeWas]

Description

This PR introduces improvements for the trace computation:

1. Adds a compute table for storing results of eliminated nodes during (partial) trace computation

• this allows the full trace computation to scale linearly with the number of nodes
• however, the partial trace computation still scales with the number of paths in the DD if the bottom qubits are to be eliminated: non-eliminated nodes cannot be stored in the compute table, as this would prevent their proper elimination in subsequent trace calls

2. Normalizes the result

Fixes #336

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.6%. Comparing base (0e4ff9e) to head (601edfa).
Report is 110 commits behind head on main.

Files with missing lines	Patch %	Lines
include/mqt-core/dd/Package.hpp	95.8%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #628     +/-   ##
=======================================
- Coverage   91.6%   91.6%   -0.1%     
=======================================
  Files        148     148             
  Lines      14736   14755     +19     
  Branches    2366    2369      +3     
=======================================
+ Hits       13511   13522     +11     
- Misses      1225    1233      +8     

Flag	Coverage Δ
cpp	91.3% <95.8%> (-0.1%)	⬇️
python	99.7% <ø> (ø)

Files with missing lines	Coverage Δ
include/mqt-core/dd/Package.hpp	97.4% <95.8%> (-0.3%)	⬇️

... and 3 files with indirect coverage changes

[burgholzer]

Many thanks for your work on this and for the clear code comments. These are highly appreciated!
I looked through all the changes here and you'll find my comments inline. Some are just minor suggestions that you can quickly incorporate. Some might take a little bit of work, but I think it shouldn't be too bad.

[burgholzer]

Many thanks for all your work on this. Especially, for writing thorough tests! ✅

I just pushed some finishing touches, which are mostly stylistic/minor. After CI is all green, this is good to go 🚀