Use new __traits(classInstanceAlignment)

[kinke]

No description provided.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✗	16508	normal	Alignment of class members is not respected. Affects new, scoped and classInstanceAlignment.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8459"

[ljmf00]

I didn't read the issue carefully before merging this and Stanislav Blinov mentioned there about creating separate issues for Phobos. Perhaps it is required to create separate issues for Phobos? Sorry for my lack of attention 😢