fix(backend): We can renote pure renote (#12171)

* chore: make pure renote detection an function

* fix: we can renote pure renote

* docs(changelog): リノートをリノートできるのを修正

* fix: remaining debug log

* chore: move isPureRenote to misc

* chore: make isPureRenote type guard

* chore: use isPureRenote in other places

* fix CHANGELOG

* style: fix lint

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Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>