Backport go-gitea#24936

If enabled show a clickable label in the comment. A click on the label
opens the Conversation tab with the comment focussed - there you're able
to view the old diff (or original diff the comment was created on).

**Screenshots**

![image](https://github.com/go-gitea/gitea/assets/1135157/63ab9571-a9ee-4900-9f02-94ab0095f9e7)

![image](https://github.com/go-gitea/gitea/assets/1135157/78f7c225-8d76-46f5-acfd-9b8aab988a6c)

When resolved and outdated:

![image](https://github.com/go-gitea/gitea/assets/1135157/6ece9ebd-c792-4aa5-9c35-628694e9d093)

Option to enable/disable this (stored in user settings - default is
disabled):

![image](https://github.com/go-gitea/gitea/assets/1135157/ed99dfe4-76dc-4c12-bd96-e7e62da50ab5)

![image](https://github.com/go-gitea/gitea/assets/1135157/e837a052-e92e-4a28-906d-9db5bacf93a6)

fixes go-gitea#24913

---------

Co-authored-by: silverwind <me@silverwind.io>