Fix issue 19902 - hasElaborateCopyConstructor doesn't know about copy…

[pbackus]

… constructors

Uses the new __traits from dlang/dmd#10528.

Previously: #2709

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19902	regression	hasElaborateCopyConstructor doesn't know about copy constructors

Testing this PR locally

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

dub fetch digger
dub run digger -- build "stable + druntime#2911"

[edi33416]

LGTM

[TurkeyMan]

There's no negative test in this PR. Regressions that produce false-positives may be missed.

[MoonlightSentinel]

FYI: Phobos forwards to this implementation and has some additional tests, see https://github.com/dlang/phobos/blob/79cc44b8f5c25ea8be6a254171b17f3606465c1a/std/traits.d#L3665-L3686

[TurkeyMan]

👍