Update aligned allocator definition for C++20 compiler supports

[mlxd]

Context: The allocator definition is incompatible with many C++20 compilers (MacOS on CF, G++ 13+). This PR updates the allocator and associated use to be compliant and pass clang-tidy validations.

Description of the Change: Update allocator definition and use.

Benefits: Fixes build issues on modern compilers.

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

Merging #438 (4ef0598) into master (8c6657e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #438   +/-   ##
=======================================
  Coverage   99.82%   99.82%           
=======================================
  Files          50       50           
  Lines        4667     4667           
=======================================
  Hits         4659     4659           
  Misses          8        8           

Impacted Files	Coverage Δ
pennylane_lightning/src/util/Memory.hpp	100.00% <ø> (ø)
pennylane_lightning/_version.py	100.00% <100.00%> (ø)
pennylane_lightning/src/simulator/Observables.hpp	100.00% <100.00%> (ø)

[chaeyeunpark]

Seems like the CI is currently using appleclang.

[mlxd]

Seems like the CI is currently using appleclang.

I added a copy of the older CI https://github.com/PennyLaneAI/pennylane-lightning/actions/runs/4734291625/jobs/8403582700?pr=438
Still fails with the changes.

[chaeyeunpark]

Do we want to use Appleclang? or brew installed newer clang-16?

[mlxd]

Do we want to use Appleclang? or brew installed newer clang-16?

Ideally we should be able to build with both, but it is preferable to favour brew install clang-16 here, as it will also be comparable on the conda forge ecosystem. The older clang-16 build is checked in as a separate CI yaml file with the word alloc appended to differentiate from the current MacOS clang builder.

[chaeyeunpark]

I don't think we can support applclang as it does not support most of the C++20 features we are using yet. Still, the CI is currently using appleclang. In https://github.com/PennyLaneAI/pennylane-lightning/actions/runs/4734291625/jobs/8403584114?pr=438, you can see

    -- The CXX compiler identification is AppleClang 13.0.0.13000029

[vincentmr]

FYI, the alligned_alloc issue I had in my PLL-Kokkos feedstock PR was resolved by this patch. I am wondering whether we should refactor the setup.py files to make less assumptions about what is found and not in the environment, and pass what is needed through CMAKE_ARGS, say. Forcing compilers, libs, programs and versions in the Actions files could make it more obvious when some defaults change.

[vincentmr]

Build issue seems fixed on Conda-Forge. Thanks guys!

[vincentmr]

Looks good to me! I derived a patch from this that is already in prod on CF.

[AmintorDusko]

I have some comments and questions.

[AmintorDusko]

Thank you for the fix, and for addressing my questions.

[AmintorDusko]

@mlxd, please remember to update the changelog.