Fix soundness issue in with `UnsafeRef<T>` · Amanieu/intrusive-rs@5c1cf18

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions-rs/toolchain@v1, actions-rs/cargo@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v2, actions-rs/toolchain@v1, actions-rs/cargo@v1. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

elided lifetime has a name

method `unwrap_unchecked` is never used

`intrusive-collections` (lib) generated 2 warnings

`intrusive-collections` (lib test) generated 2 warnings (2 duplicates)

elided lifetime has a name

the feature `const_fn_trait_bound` has been stable since 1.61.0 and no longer requires an attribute to enable

method `unwrap_unchecked` is never used

`intrusive-collections` (lib) generated 3 warnings

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