move jquery-datetimepicker to npm/webpack (#10713)

- update to latest version and move to npm
- adapt for api changes and css class rename
- add specificity to arc-green rules as dependency css now loads later
- use imports-loader to make it load correctly
- fix some wrong paths in librejs

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/js/features/datetimepicker.js

@@ -0,0 +1,8 @@
+export default async function initDateTimePicker(locale) {
+  await Promise.all([
+    import(/* webpackChunkName: "datetimepicker" */'jquery-datetimepicker'),
+    import(/* webpackChunkName: "datetimepicker" */'jquery-datetimepicker/build/jquery.datetimepicker.min.css'),
+  ]);
+
+  $.datetimepicker.setLocale(locale);
+}