Move emplaceRef to core/internal

[edi33416]

Move emplaceRef to core.internal.lifetime so we can remove the code duplication from Phobos.
emplaceRef is intentionally non-ddoc'ed

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[thewilsonator]

Why does this need to be moved for phobos deduplication?

[thewilsonator]

At the very least it should be imported by core.lifetime

cc'ing @TurkeyMan

[edi33416]

Why does this need to be moved for phobos deduplication?

emplaceRef is used internally in various parts of Phobos. See @wilzbach 's comment here

[PetarKirov]

Moving to core.internal is good as it's the place for public, yet intended for internal use, functions.
A "simpler" way would be to make emplaceRef public and leave it in core.lifetime, but I don't think we should advertise emplaceRef as part of the public API, or at least not yet.

[wilzbach]

Thanks!

[wilzbach]

I don't think we should advertise emplaceRef as part of the public API, or at least not yet

Imho it's not going to go anywhere anyhow (like emplace), so we could just start to officially lock us in ;-)
Though, of course core.internal is safer and solves the duplication problem.

[edi33416]

Why does this need to be moved for phobos deduplication?

At the very least it should be imported by core.lifetime

cc'ing @TurkeyMan

I chose local imports against top level ones so a user won't pay the import cost if he doesn't use emplace.