Revert "chore: Extract sidebar item injection token into separate package"

This reverts commit 8ac66380ad.

packages/core/package.json

@@ -290,7 +290,6 @@
     "@k8slens/application-for-electron-main": "^6.5.0-alpha.0",
     "@k8slens/button": "^1.0.0-alpha.5",
     "@k8slens/cluster-settings": "^6.5.0-alpha.1",
-    "@k8slens/cluster-sidebar": "^1.0.0-alpha.0",
     "@k8slens/error-boundary": "^1.0.0-alpha.5",
     "@k8slens/event-emitter": "^1.0.0-alpha.1",
     "@k8slens/kubectl-versions": "^1.0.0-alpha.0",