Refactor startup deprecation messages (#30305)

It doesn't change logic, it only does:

1. Rename the variable and function names
2. Use more consistent format when mentioning config section&key
3. Improve some messages

routers/web/admin/config.go

@@ -165,7 +165,7 @@ func Config(ctx *context.Context) {
 
 	ctx.Data["Loggers"] = log.GetManager().DumpLoggers()
 	config.GetDynGetter().InvalidateCache()
-	prepareDeprecatedWarningsAlert(ctx)
+	prepareStartupProblemsAlert(ctx)
 
 	ctx.HTML(http.StatusOK, tplConfig)
 }