Missing icon and row for column pinning in Tree grid row pinning sample

[valadzhov]

1. Open the sample and examine it https://staging.infragistics.com/products/ignite-ui-blazor/blazor/components/grids/tree-grid/row-pinning#via-extra-column-with-icon
   The text and the code snippet describe a column with a special icon for column pinning but not such icon (or column) is found.

[tishko0]

It also needs this one to work:
https://infragistics.visualstudio.com/NetAdvantage/_git/dev-tools/pullrequest/14403