Rollup merge of #136923 - samueltardieu:push-vxxqvqwspssv, r=davidtwco

Lint `#[must_use]` attributes applied to methods in trait impls

The `#[must_use]` attribute has no effect when applied to methods in trait implementations. This PR adds it to the unused `#[must_use]` lint, and cleans the extra attributes in portable-simd and Clippy.

Author: matthiaskrgr