🚨 Run clang-tidy on MLIR subproject, switch to LLVM@20, and update to CMake >= 3.24

[burgholzer]

Description

This pull request enables running clang-tidy for the MLIR subproject and updates the project to use LLVM version 20. This enhances code quality checks and aligns the project with the latest LLVM updates. It is also the same version currently shipped with CLion.

In addition, this PR raises the minimum supported CMake version to 3.24, which brings in several improvements:

• Better FetchContent functionality (no more backwords-compatible workarounds)
• Support for file sets which can be used to automatically install header files associated with a target.
• CMAKE_VERIFY_INTERFACE_HEADER_SETS to enable build rules that verify all headers in header sets can be used on their own.

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 84.04255% with 15 lines in your changes missing coverage. Please review.

Project coverage is 92.5%. Comparing base (96b46fc) to head (4642a92).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
include/mqt-core/dd/Operations.hpp	42.8%	4 Missing ⚠️
src/dd/Simulation.cpp	0.0%	4 Missing ⚠️
src/ir/operations/StandardOperation.cpp	0.0%	3 Missing ⚠️
src/circuit_optimizer/CircuitOptimizer.cpp	60.0%	2 Missing ⚠️
src/ir/QuantumComputation.cpp	95.2%	1 Missing ⚠️
src/ir/operations/SymbolicOperation.cpp	50.0%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (84.0%) is below the target coverage (90.0%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #879     +/-   ##
=======================================
+ Coverage   92.3%   92.5%   +0.2%     
=======================================
  Files        145     145             
  Lines      13850   13841      -9     
  Branches    2107    2107             
=======================================
+ Hits       12789   12815     +26     
+ Misses      1061    1026     -35     

Flag	Coverage Δ
cpp	92.3% <84.0%> (+0.2%)	⬆️
python	98.4% <ø> (ø)

Files with missing lines	Coverage Δ
include/mqt-core/datastructures/Layer.hpp	89.1% <ø> (ø)
...nclude/mqt-core/datastructures/UndirectedGraph.hpp	100.0% <ø> (ø)
include/mqt-core/dd/Complex.hpp	100.0% <100.0%> (ø)
include/mqt-core/dd/ComplexValue.hpp	87.5% <100.0%> (ø)
include/mqt-core/dd/ComputeTable.hpp	100.0% <ø> (ø)
include/mqt-core/dd/DDDefinitions.hpp	100.0% <ø> (ø)
include/mqt-core/dd/NoiseFunctionality.hpp	100.0% <ø> (ø)
include/mqt-core/dd/Package.hpp	96.7% <ø> (ø)
include/mqt-core/dd/RealNumber.hpp	100.0% <ø> (ø)
...lude/mqt-core/dd/StochasticNoiseOperationTable.hpp	92.5% <ø> (ø)
... and 51 more

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[burgholzer]

@flowerthrower @ystade just venting my frustration here. Of course the LLVM set up would be making problems with clang-tidy.. it's not like that is actually part of the same monorepository..
I'll play around with this a little more and try to make it not complain, but at some point I am just going to put // IWYU pragma: ignore etc. in the respective parts and merge this to move it forward.