report improper_ctypes lints from external macros

[im-lunex]

FFI safety belongs to the types being defined, not the macro generating the extern function. Currently, cross-crate macros trigger a heuristic that silently drops these warnings.

This PR enables report_in_external_macro for improper_ctypes and improper_ctypes_definitions. Warnings now emit as expected, while code suggestions stay suppressed for external spans.

uses_power_alignment is untouched as it follows a separate emission path.

Fixes #160862

[rustbot]

r? @khyperia

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[khyperia]

thanks for the PR, we appreciate it! ❤️

uses_power_alignment is untouched as it follows a separate emission path.

hmm, why are you mentioning this?

[im-lunex]

when I was adding report_in_external_macro to the two lints.. saw USES_POWER_ALIGNMENT sitting just below them in the same pass. it confused me for a second on whether I should touch it too then realized it was completely unrelated... but taught it would be better to add this for more clarification...

[khyperia]

right, thanks! this looks good to me, but I'm unsure of the review process for lint changes like this, especially because the issue was just created and you posted a PR to fix it immediately, and am inexperienced with estimating lint ecosystem impact/etc. - e.g. if the macro comes from a third party crate you can't easily update. So, rerolling for that perspective, and I'll listen/learn for next time~

@rustbot reroll