fix(UnusedImport): detect named companion objects correctly (#9005)

* fix(UnusedImport): detect named companion objects correctly

Previously, the rule only recognized companion objects with the default
name "Companion" when determining if a class reference is used. This
caused false positives when referencing classes with named companion
objects (e.g., `CoroutineDispatcher` which has `companion object Key`).

The fix uses `classKind == KaClassKind.COMPANION_OBJECT` to properly
detect all companion objects regardless of their name.

Fixes #8989

* refactor(UnusedImport): simplify companion object detection

Use a when expression instead of intermediate variables.

---------

Co-authored-by: Claude <noreply@anthropic.com>

Prepare Release 2.0.0-alpha.1 (#8788)

`Detektion` is a `class` now instead of an `interface` (#8580)

* Improve code

* Detektion class

Prepare Release 1.23.8 (#7976)

Prepare Release 1.23.7 (#7608)

Prepare Release 1.23.6 (#7082)

Prepare Release 1.23.5 (#6921)

Prepare Release 1.23.4 (#6650)

Prepare release 1.23.3 (#6582)

Prepare release 1.23.2 (#6574)