Rollup merge of #159181 - quiode:mem--forget-implicit-writes, r=RalfJung

add rustc_no_writable to mem::forget and structs it uses

This builds upon https://github.com/rust-lang/rust/pull/155207 and is similar to https://github.com/rust-lang/rust/pull/157202. It adds the `#[rustc_no_writable]` attribute to `mem::forget` and the `MaybeDangling` and `ManuallyDrop`. This makes Miri with Tree Borrows and implicit writes no longer report UB for a test in `derive_more`.
As the pattern itself is quite unclean, and I have not seen `mem::forget` to cause trouble before with implicit writes, I'm not sure how much sense it makes to add it to `mem::forget`. The test works unter Tree Borrows, but fails already for Stacked Borrows. Thus I would be happy for some guidance if the attribute makes sense here @RalfJung  @JoJoDeveloping.
tree: a290c5e38073a4070aa7a78fed195ccb09c2cbaa
  1. .github/
  2. compiler/
  3. library/
  4. LICENSES/
  5. src/
  6. tests/
  7. .clang-format
  8. .editorconfig
  9. .git-blame-ignore-revs
  10. .gitattributes
  11. .gitignore
  12. .gitmodules
  13. .ignore
  14. .mailmap
  15. bootstrap.example.toml
  16. Cargo.lock
  17. Cargo.toml
  18. CODE_OF_CONDUCT.md
  19. configure
  20. CONTRIBUTING.md
  21. COPYRIGHT
  22. INSTALL.md
  23. LICENSE-APACHE
  24. license-metadata.json
  25. LICENSE-MIT
  26. package.json
  27. README.md
  28. RELEASES.md
  29. REUSE.toml
  30. rust-bors.toml
  31. rustfmt.toml
  32. triagebot.toml
  33. typos.toml
  34. x
  35. x.ps1
  36. x.py
  37. yarn.lock
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