Misc clippy_dev changes

[Jarcho]

changelog: none

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[samueltardieu]

The output of a failure in cargo dev lint is changed for the worse.

Also, the commit message first line of the first commit is a bit too long and gets wrapped into the detailed description.

[dswij]

Thanks for this! Good to merge after addressing the merge conflict @Jarcho (and also, apologies for the delay in reviewing).