Substituing quickersort with pdqsort
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I have been working on issue number #15244. I have substituted quickersort with pdqsort in the style component. The changes I made affect: Cargo.toml, stylist.rs and lib.rs (all of them are in /components/style).
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#15244 (github issue number if applicable).
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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because both library expose the same functionality, they differ in permance.
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This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15269)
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