None of the features of `unrolled/render` package is used.
The Golang builtin "html/template" just works well. Then we can improve
our HTML render to resolve the "$.root.locale.Tr" problem as much as
possible.
Next step: we can have a template render pool (by Clone), then we can
inject global functions with dynamic context to every `Execute` calls.
Then we can use `{{Locale.Tr ....}}` directly in all templates , no need
to pass the `$.root.locale` again and again.
Replace #23350.
Refactor `setting.Database.UseMySQL` to
`setting.Database.Type.IsMySQL()`.
To avoid mismatching between `Type` and `UseXXX`.
This refactor can fix the bug mentioned in #23350, so it should be
backported.
wxiaoguang
Jason Song
Lunny Xiao