[Date / Date Range Picker] Dropdown/dialog with the calendar picker is not properly styled

[yradoeva]

The footer containing the action buttons in the dropdown/dialog calendar picker of the Date picker / Date range picker is not properly styled - missing background and top border.
The dropdown/dialog itself is missing border radius and elevation/shadow.

Steps to reproduce:

1. Open Ignite UI Angular demo repo
2. In the Date picker / Date range picker example click on the toggle icon to open the dropdown/dialog with the calendar picker

Result (the page's background is set to lightblue for better visibility):

Material light mode (similar in dark mode)
Dropdown

Dialog

The same issue is observed also in Fluent, Bootstrap, Indigo, light and dark mode.

Expected:
Date Picker Handoff
Data Range Picker Handoff