docs(changelog): note const-eval pointer copy scope

[PLeVasseur]

Summary

• Record no-change for const-eval pointer byte copying because FLS does not specify byte-level const-eval memory/provenance semantics; capturing this would require a broader const-eval specification.
• Closes [Change]: [1.93] During const-evaluation, support copying pointers byte-by-byte rust-lang/fls#648

Reference alignment

• No Rust Reference PR linked for const-eval: fix and re-enable pointer fragment support rust-lang/rust#148259

Non-normative references

• https://rustc-dev-guide.rust-lang.org/const-eval/interpret.html#memory
• https://rust-lang.github.io/unsafe-code-guidelines/glossary.html#abstract-byte
• https://rust-lang.github.io/unsafe-code-guidelines/glossary.html#pointer-provenance

Excerpts

• rustc-dev-guide const-eval/interpret.html#memory

  Such an `Allocation` is basically just a sequence of `u8` storing the value of each byte in this allocation.
  ... a `Pointer` consists of a pair of an `AllocId` ... and an offset into the allocation.
  ... we want to store a `Pointer` into an `Allocation`: ... the `relocation` field ... stores the byte offset
  as a bunch of `u8`, while its `AllocId` gets stored out-of-band.
  

• UCG glossary glossary.html#abstract-byte

  Another piece of shadow state is pointer provenance ... implies that abstract bytes must be able to carry provenance.
  ... Init(u8, Option<Provenance>)
  

• UCG glossary glossary.html#pointer-provenance

  The provenance of a pointer is used to distinguish pointers that point to the same memory address ...
  

Testing

• ./make.py

[tshepang]

was this meant to be opened against upstream