Re-export some iterators from core in std

[mbartlett21]

These iterators seem to have been forgotten to be re-exported from std (through alloc)

These are stable:

core::slice::{SplitInclusive, SplitInclusiveMut}

This one is still unstable:

core::slice::EscapeAscii (cc #77174)

[rust-highfive]

r? @kennytm

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[kennytm]

error[E0658]: use of unstable library feature 'inherent_ascii_escape'
   --> library/alloc/src/slice.rs:112:9
    |
112 | pub use core::slice::EscapeAscii;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #77174 <https://github.com/rust-lang/rust/issues/77174> for more information
    = help: add `#![feature(inherent_ascii_escape)]` to the crate attributes to enable

[mbartlett21]

This was actually incorrect. It hadn't been picked up, since it was across crates.

[kennytm]

@bors r+ rollup

[bors]

📌 Commit ed63c71 has been approved by kennytm

[bors]

⌛ Testing commit ed63c71 with merge d22dd65...

[bors]

☀️ Test successful - checks-actions
Approved by: kennytm
Pushing d22dd65 to master...

[rust-timer]

Finished benchmarking commit (d22dd65): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression