[DataGrid] Use the new toolbar by default in v8

[cherniavskii]

• Use the new toolbar from [DataGrid] New Toolbar component #14611 by default
• Stop exporting GridToolbar component
• Add a new prop to enable toolbar (instead of slots={{ GridToolbar }}) – e.g. showToolbar [DataGrid] Add showToolbar prop to enable default toolbar #16687

[cherniavskii]

@joserodolfofreitas What do you think? Should we include this in v8?

[joserodolfofreitas]

@cherniavskii, Yes, let's include the new toolbar as default.
I don't think anyone will prefer the old look, but I suppose we could simply create a recipe once (if) that demand arise.

[KenanYusuf]

Blocked by #14611