Add new lint: `ref_as_ptr`
Fixes#10130
Added new lint `ref_as_ptr` that checks for conversions from references to pointers and suggests using `std::ptr::from_{ref, mut}` instead.
The name is different than suggested in the issue (`as_ptr_cast`) since there were some other lints with similar names (`ptr_as_ptr`, `borrow_as_ptr`) and I wanted to follow the convention.
Note that this lint conflicts with the `borrow_as_ptr` lint in the sense that it recommends changing `&foo as *const _` to `std::ptr::from_ref(&foo)` instead of `std::ptr::addr_of!(foo)`. Personally, I think the former is more readable and, in contrast to `addr_of` macro, can be also applied to temporaries (cf. #9884).
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changelog: New lint: [`ref_as_ptr`]
[#12087](https://github.com/rust-lang/rust-clippy/pull/12087)
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