Fix: enum prefix/suffix matching lint should not fire when variant has the same name as the container type

[lynzrand]

Fixes #16895

This PR fixes the issue where enum variant prefix/suffix matches container type is fired, when the variant have exactly the same name as the container type.

Changes TL;DR: Moved the prefix/suffix checking functions into the ItemNameRepetetions type and added a check that asserts non-equality between the variant name and container name.

Note: The issue hasn't been triaged when this PR was submitted. Feel free to close it if it's a false-false-positive.

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changelog: [enum_variant_names] no longer fires when the enum variant name equals the container name

[rustbot]

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[github-actions]

Lintcheck changes for 038dbe3

Lint	Added	Removed	Changed
clippy::enum_variant_names	0	2	2

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