Display deprecated warning in admin panel pages as well as in the log file (#26094)

This PR includes #26007 's changes but have a UI to prompt administrator
about the deprecated settings as well as the log or console warning.
Then users will have enough time to notice the problem and don't have
surprise like before.

<img width="1293" alt="图片"
src="https://github.com/go-gitea/gitea/assets/81045/c33355f0-1ea7-4fb3-ad43-cd23cd15391d">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/admin/config.go

@@ -171,6 +171,8 @@ func Config(ctx *context.Context) {
 
 	ctx.Data["Loggers"] = log.GetManager().DumpLoggers()
 
+	prepareDeprecatedWarningsAlert(ctx)
+
 	ctx.HTML(http.StatusOK, tplConfig)
 }