Do not trigger clippy::exit when expression comes from an external macro

[samueltardieu]

changelog: [exit]: do not trigger when the call to exit() comes from an external macro

Fixes #17082

[rustbot]

r? @llogiq

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[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.