DatePicker (opened) rendering differences (contains .k-content & .k-scrollable)

[NickIliev]

Description

The rendering for DatePicker in KendoReact uses CSS classes like k-content and k-scrollable that are not part of the unified rendering as per the source of truth tests:
https://github.com/telerik/kendo-themes/blob/develop/tests/datepicker/datepicker-opened.html

Steps To Reproduce

Open the DatePicker demo at https://www.telerik.com/kendo-react-ui/components/dateinputs/datepicker and inspect the produced rendering.

Then compare it with the source of truth tests

https://github.com/telerik/kendo-themes/blob/develop/tests/datepicker/datepicker-opened.html

Reported through multiple tickets in ThemeBuilder as per telerik/themebuilder#82

There are possibly other rendering differences as well as per telerik/themebuilder#101

Actual Behavior

Adds wrappers that are not present in the expected rendering

Expected Behavior

To render the DatePicker as per the source of truth so that the produced styles from the Kendo theme are fully compatible (ThemeBuilder-related)