Implement lint for black_boxing ZSTs

[xonx4l]

In the PR lint for black_boxing ZSTs is implemented as discussed in #137658

This PR implements a new lint which warns when std::hint::black_box is called with a Zero-Sized Type (ZST).

Changes:
Added #[rustc_diagnostic_item = "black_box"] to library/core/src/hint.rs.
Implemented a LateLintPass to detect calls to black_box where the argument's layout is a ZST.

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[rust-log-analyzer]

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  |
  = note: using it is strongly discouraged
  = note: `#[warn(internal_features)]` on by default

warning: `black_box` on zero-sized callable `fn(u32, u32) -> u32 {add}` has no effect on call opacity
    --> compiler/rustc_lint/src/builtin.rs:3132:18
     |
3132 |     let add_bb = black_box(add);
     |                  ^^^^^^^^^^---^
     |                            |
     |                            zero-sized callable passed here
     |
     = note: zero-sized callable values have no runtime representation, so the call still targets the original function directly
     = help: coerce to a function pointer and call `black_box` on that pointer instead
     = note: `#[warn(black_box_zst_calls)]` on by default

warning: 2 warnings emitted

Test compiled successfully, but it's marked `compile_fail`.
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