Prereq3 for async drop - LangItem registration for async_drop_in_place()::{{closure0}}

[azhogin]

This is subpart 3 PR of #123948, just for review purposes.
We have async_drop_in_place lang item for async fn async_drop_in_place<T>(...).

#[lang = "async_drop_in_place"]
pub async unsafe fn async_drop_in_place<T: ?Sized>(_to_drop: *mut T) { ... }

But we also need to generate shim for its returning value - coroutine async_drop_in_place<T>::{{closure0}}.
So, we need to bind some lang item to it. This patch registers LangItem::AsyncDropInPlacePoll for coroutine, when its constructor function is LangItem::AsyncDropInPlace.

Review only last commit, based on previous PR #129736

[rustbot]

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This PR changes MIR

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