Prepare for uplift of drop-bounds lint

[taiki-e]

rust-lang/rust#75699 uplifts clippy's drop_bounds lint to rustc.
If the implementation is the same as clippy, the code generated by the macro will also be warned (this behavior is probably correct for this lint), and pin-project(-lite) users will be affected by this.

Once rust-lang/rust#75699 or rust-lang/compiler-team#347 merged (or approved), it would be nice to be able to create a release including a patch that allows this lint.

[taiki-e]

I'll merge this and publish new releases of pin-project and pin-project-lite, when FCP of rust-lang/compiler-team#347 is finished.

FYI @notriddle

[taiki-e]

Done in pin-project 0.4.25 and pin-project-lite 0.1.10.

[taiki-e]

If the implementation is the same as clippy

The code generated by the external macro doesn't actually seem to get a warning (probably because LintContext::struct_span_lint is used). So this probably wasn't really needed.