Auto merge of #110353 - the8472:in-place-flatten-chunks, r=cuviper

Expand in-place iteration specialization to Flatten, FlatMap and ArrayChunks

This enables the following cases to collect in-place:

```rust
let v = vec![[0u8; 4]; 1024]
let v: Vec<_> = v.into_iter().flatten().collect();

let v: Vec<Option<NonZeroUsize>> = vec![NonZeroUsize::new(0); 1024];
let v: Vec<_> = v.into_iter().flatten().collect();

let v = vec![u8; 4096];
let v: Vec<_> = v.into_iter().array_chunks::<4>().collect();
```

Especially the nicheful-option-flattening should be useful in real code.

1 files changed, 1 insertions, 0 deletions

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 59b2433ca74..0af3ac38ee5 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -154,6 +154,7 @@
 #![feature(std_internals)]
 #![feature(str_internals)]
 #![feature(strict_provenance)]
+#![feature(trusted_fused)]
 #![feature(trusted_len)]
 #![feature(trusted_random_access)]
 #![feature(try_trait_v2)]