Lint `collapsible_str_replace`

[nahuakang]

fixes #6651

changelog: [`collapsible_str_replace`]: create new lint `collapsible_str_replace`

If you added a new lint, here's a checklist for things that will be checked during review or continuous integration.

• [x] Followed [lint naming conventions][lint_naming]
• [x] Added passing UI tests (including committed .stderr file)
• [x] cargo test passes locally
• [ ] Executed cargo dev update_lints
• [x] Added lint documentation
• [x] Run cargo dev fmt

[rust-highfive]

r? @flip1995

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[bors]

:umbrella: The latest upstream changes (presumably #9264) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

:umbrella: The latest upstream changes (presumably #8957) made this pull request unmergeable. Please resolve the merge conflicts.

[flip1995]

@bors r+

Thanks! That implementation turned out nicely!

[bors]

:pushpin: Commit b070b4045f348f9222008270a435bda17b048c15 has been approved by flip1995

It is now in the queue for this repository.

[bors]

:hourglass: Testing commit b070b4045f348f9222008270a435bda17b048c15 with merge 5820addb240ddcf13712be686c141a3d00ae792a...

[nahuakang]

@flip1995 @xFrednet Thank you both for your patience and help 🙏 It's absolutely just wonderful to come back to the project and receive so much support and help ❤️

[bors]

:sunny: Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test Approved by: flip1995 Pushing 5820addb240ddcf13712be686c141a3d00ae792a to master...