suspicious_double_ref_op: report unadjusted return type

[qaijuang]

suspicious_double_ref_op uses the adjusted expression type to distinguish a no-op call from a double-reference operation. When the result is used as another method's receiver, that type can include the parent method's receiver adjustment.

For example, file.clone().write(&[]) reports that clone returns &mut &File, even though it returns &File.

This PR continues to use the adjusted type for lint classification, but now uses the method call's unadjusted type in the diagnostic. The same issue affects .deref(), so the regression test covers both operations.

Fixes #146227

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