Filtering icon of DropDowns doesn't have padding

[tswetti]

Describe the bug
Initially reported here - telerik/kendo-angular#4294

The filtering icon of the DropDownTree and MultiSelectTree does not have padding in Kendo Angular due to the icon wrapper:

The DropDownList has padding as expected.

The cause of the issue could be either:

• The CSS selector that applies the padding doesn't take into consideration .k-icon-wrapper-host
• Both DropDowns lack the .k-input-icon class that is present in the DropDownList

To reproduce
https://www.telerik.com/kendo-angular-ui/components/dropdowns/multiselecttree/filtering/#toc-built-in-filtering

Expected behavior
The filtering icon to have padding:

Affected suites

• Kendo UI for Angular