♻️ Refactor and improve register handling

[burgholzer]

Description

This PR originated out of working on #729. It refactors certain aspects of how registers are handled in MQT Core. In particular:

• Registers are now no longer typedefs, but proper structs with some convenience methods that make the code more legible.
• Classic-controlled operations now either take a full ClassicalRegister or a single bit. This closely matches the kind of operations we actually support and defines some errors out of existance.
• The QASM dump functionality has been made more robust and can now, in principle, handle discontinuous registers.

In addition to that,

• a couple of redundant functions have been removed
• some general typedefs have been moved to more explicit places, and
• some clang-tidy recommendations have been implemented.

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 91.46341% with 35 lines in your changes missing coverage. Please review.

Project coverage is 92.2%. Comparing base (bea8448) to head (ef7b2ec).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ir/QuantumComputation.cpp	94.3%	8 Missing ⚠️
include/mqt-core/dd/Operations.hpp	50.0%	6 Missing ⚠️
src/ir/operations/StandardOperation.cpp	78.5%	6 Missing ⚠️
src/dd/Simulation.cpp	54.5%	5 Missing ⚠️
src/circuit_optimizer/CircuitOptimizer.cpp	95.1%	4 Missing ⚠️
include/mqt-core/ir/Register.hpp	89.6%	3 Missing ⚠️
src/algorithms/Grover.cpp	75.0%	1 Missing ⚠️
src/ir/operations/ClassicControlledOperation.cpp	95.4%	1 Missing ⚠️
src/ir/operations/SymbolicOperation.cpp	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #807     +/-   ##
=======================================
+ Coverage   92.0%   92.2%   +0.1%     
=======================================
  Files        125     126      +1     
  Lines      13828   13826      -2     
  Branches    2153    2153             
=======================================
+ Hits       12735   12757     +22     
+ Misses      1093    1069     -24     

Flag	Coverage Δ
cpp	92.0% <91.4%> (+0.1%)	⬆️
python	99.7% <ø> (ø)

Files with missing lines	Coverage Δ
include/mqt-core/Definitions.hpp	76.4% <ø> (ø)
include/mqt-core/ir/QuantumComputation.hpp	100.0% <100.0%> (ø)
include/mqt-core/ir/operations/AodOperation.hpp	77.7% <ø> (ø)
...-core/ir/operations/ClassicControlledOperation.hpp	96.9% <100.0%> (+0.1%)	⬆️
...clude/mqt-core/ir/operations/CompoundOperation.hpp	100.0% <ø> (ø)
...ude/mqt-core/ir/operations/NonUnitaryOperation.hpp	100.0% <ø> (ø)
include/mqt-core/ir/operations/Operation.hpp	79.2% <100.0%> (+0.2%)	⬆️
...clude/mqt-core/ir/operations/StandardOperation.hpp	100.0% <ø> (ø)
...clude/mqt-core/ir/operations/SymbolicOperation.hpp	100.0% <ø> (ø)
src/algorithms/BernsteinVazirani.cpp	100.0% <100.0%> (ø)
... and 17 more

... and 1 file with indirect coverage changes