Backport move(Emplace) fixes from Phobos

[MoonlightSentinel]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20869	enhancement	std.algorithm.mutation : move is overly trusting of opPostMove

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 + druntime#3133"

[kinke]

I confess I didn't know this already exists. Good lord, another half-complete feature (copy ctors...), as the compiler AFAIK doesn't emit any calls for the (many) implicit moves...

[radcapricorn]

Didn't this __move_post_blt and opPostMove business become a non-starter due to qualifier hell?

[MoonlightSentinel]

It certainly needs more work but the druntime/phobos versions of these functions shouldn't differ.

[radcapricorn]

I'll just ping @RazvanN7 in hopes of clarifying the status of __move_post_blt. If it's dead, quite a few changes would need to be made.

[12345swordy]

Looks good to me.

[12345swordy]

cc @thewilsonator

[radcapricorn]

I'd rather if this was looked over wrt __move_post_blt and the de-facto status of DIP1014.

[MoonlightSentinel]

Ping, move should not have different in druntime and Phobos (regardless of the state of opPostMove)