Move array dup properties from object.d to core.internal

[JinShil]

Followup to #2647, #2644, #2643, and #2634

This is a continuation of work to clean up object.d. It's just a cut-and-paste with the exception of getPostblit and doPostblit which were made public (though still private to druntime because it is in core.internal) so it could be used by some associative array code that still resides in object.d

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[JinShil]

Weird! All packages in buildkite pass, but the unittests in core.internal.array.duplication.d fail.

[thewilsonator]

src/core/internal/array/duplication.d(243): Error: cannot implicitly convert expression `dup(s)` of type `char[]` to `immutable(string)`
--
  | src/core/internal/array/duplication.d(268): Error: cannot implicitly convert expression `dup(m)` of type `void[]` to `immutable(void)[]`
  | src/core/internal/array/duplication.d(272): Error: cannot implicitly convert expression `dup(s)` of type `shared(void)[]` to `immutable(void)[]`
  | src/core/internal/array/duplication.d(243): Error: cannot implicitly convert expression `dup(s)` of type `char[]` to `immutable(string)`
  | src/core/internal/array/duplication.d(268): Error: cannot implicitly convert expression `dup(m)` of type `void[]` to `immutable(void)[]`
  | src/core/internal/array/duplication.d(272): Error: cannot implicitly convert expression `dup(s)` of type `shared(void)[]` to `immutable(void)[]`

[JinShil]

@thewilsonator. Thanks. I see the error message, but any idea why it is occurring? All I did was move the code.

[thewilsonator]

Dunno, but it seems that all of those should be idups.

[JinShil]

it seems that all of those should be idups.

Line 38 explicitly says const overload to support implicit conversion to immutable (unique result, see DIP29), so there must be something else at play. Something's not right though. Just moving code shouldn't trigger this.

[thewilsonator]

IDK, try asking on slack or the NG,

[JinShil]

I don't think these symbols should be in core.internal. I think there are a couple of better ways to do this.

[PetarKirov]

@JinShil as mentioned in #2784, I think they're perfect candidates for core.array.