Address unnecessary_to_owned false positive

[smoelius]

My proposed fix for #8759 is to revise the conditions that delineate redundant_clone and unnecessary_to_owned:

        // Only flag cases satisfying at least one of the following three conditions:
        // * the referent and receiver types are distinct
        // * the referent/receiver type is a copyable array
        // * the method is `Cow::into_owned`
        // This restriction is to ensure there is no overlap between `redundant_clone` and this
        // lint. It also avoids the following false positive:
        //  https://github.com/rust-lang/rust-clippy/issues/8759
        //   Arrays are a bit of a corner case. Non-copyable arrays are handled by
        // `redundant_clone`, but copyable arrays are not.

This change causes a few cases that were previously flagged by unnecessary_to_owned to no longer be flagged. But one could argue those cases would be better handled by redundant_clone.

Closes #8759

changelog: none

[rust-highfive]

r? @llogiq

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[llogiq]

That sounds sensible. Thank you!

@bors r+

[bors]

📌 Commit 91a822c has been approved by llogiq

[bors]

⌛ Testing commit 91a822c with merge 9c78883...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 9c78883 to master...