✨ Add XX-plus-YY and XX-minus-YY gate support to ZX library

[burgholzer]

Description

This PR adds the last remaining unsupported gates to the ZX library.
In the process, it also introduces a new convenience function for integer division of parameter expressions that simplifies some code. In conjunction with #549, this also fixes #486.

Fixes #343

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: 13 lines in your changes are missing coverage. Please review.

Comparison is base (af9d20a) 91.1% compared to head (24670ee) 91.1%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #482   +/-   ##
=====================================
  Coverage   91.1%   91.1%           
=====================================
  Files        131     131           
  Lines      13667   13761   +94     
  Branches    2150    2166   +16     
=====================================
+ Hits       12451   12539   +88     
- Misses      1216    1222    +6     

Flag	Coverage Δ
cpp	90.8% <90.9%> (+<0.1%)	⬆️
python	99.5% <ø> (ø)

Files	Coverage Δ
include/mqt-core/operations/Expression.hpp	92.7% <90.0%> (-0.2%)	⬇️
src/zx/FunctionalityConstruction.cpp	93.3% <90.9%> (-1.6%)	⬇️

... and 2 files with indirect coverage changes

[pehamTom]

LGTM. I checked with the qiskit decompositions and everything seems alright with me. Just a tiny optimization but for me its fine to omit it.

Another thing that I thought of is that Z rotations can be fused with the Control of CNOTs before or after (same for X rotations and targets). But I think that happens in more places than the added gates so it can be handled separately.

[burgholzer]

LGTM. I checked with the qiskit decompositions and everything seems alright with me. Just a tiny optimization but for me its fine to omit it.

Another thing that I thought of is that Z rotations can be fused with the Control of CNOTs before or after (same for X rotations and targets). But I think that happens in more places than the added gates so it can be handled separately.

Thanks for the feedback! I remember that I even tried that from the very beginning but I was getting some kind of weird results and couldn't get tests to pass.
Now that investigated a little more, I stumbled upon #486, which is kind of unfortunate and explains the errors I got on my first try.

[burgholzer]

@pehamTom many thanks for the changes here. Nice to see this go in!
Looking forward to the next QCEC release with the additional gate support and these fixes.