Add cargo dev dogfood

[Serial-ATA]

changelog: Add cargo dev dogfood

Part of #5394

[rust-highfive]

r? @giraffate

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[xFrednet]

Thanks for working on Clippy's internal tools! Wouldn't it be simpler to add new cargo aliases instead of extending clippy_dev?

[Serial-ATA]

I'm not sure how to best handle --fix in that case.

[xFrednet]

Good point, I just have never used --fix with dogfood, and in general tbh 😅. We could have an environment value, like we have to uitest, but that feels hacky. Then I think this is a good solution! 🙃

[giraffate]

Can the document about the dogfood tests be updated?
https://github.com/rust-lang/rust-clippy/blob/master/book/src/development/basics.md#building-and-testing

[giraffate]

@bors r+

Thanks!

[bors]

📌 Commit 131770d has been approved by giraffate

[bors]

⌛ Testing commit 131770d with merge d4488a5...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing d4488a5 to master...