### Bug report

The attributes set through the "HtmlAttributes", "ContentHtmlAttributes", and "LinkHtmlAttributes"methods are not applied to the TreeView items.

### Reproduction of the problem

1. Create a TreeView and set attributes by using the "HtmlAttributes", "ContentHtmlAttributes", "LinkHtmlAttributes"methods:

@(Html.Kendo().TreeView()
    .Name("treeview-kendo2")
    .Items(treeview =>
    {
        treeview.Add().Text("My Documents")
        .SpriteCssClasses("k-icon k-i-globe")
        .Expanded(true)
        .Url("/")
        .HtmlAttributes(new { @class = "fairydust1" })
        .ContentHtmlAttributes(new { data_navigate = "navigate_content", @class = "trigger", title = "content_title" })
        .LinkHtmlAttributes(new { data_navigate = "navigate_link", @class = "trigger", title = "content_link" });
    })
)

2. Run the page and inspect the TreeView item.

### Expected/desired behavior

The attributes are serialized and rendered.

### Environment

* **Kendo UI version: 2021.2.616
* **jQuery version: 1.12.4
* **Browser: [all]