Deprecate cognitive_complexity lint

[samueltardieu]

This also deprecates the cyclomatic_complexity lint which had been renamed into cognitive_complexity back in 2019.

See discussion on Zulip.

changelog: [cognitive_complexity]: deprecated lint

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[dswij]

Are we deprecating it in this release?

[samueltardieu]

It would be for 1.90, so in about 13 weeks.

[samueltardieu]

Rebased

[LebedevRI]

Question: would there be any interest to actually have a lint that works as specified in the Cognitive Complexity spec?
I thought that this lint wasn't working as it should seeing that it did not trigger on my code where i expected it would,
and looking at it's source, yep, it's a "name squatter".

[samueltardieu]

Superseded by #15415.