Grid high density

[TeyaVes]

Do not merge until the updated rendering is addressed in all suites

closes: https://github.com/telerik/kendo-themes/issues/4004 targets: https://github.com/telerik/kendo-themes/issues/3680

needs: https://github.com/telerik/kendo-themes/pull/4047 & https://github.com/telerik/kendo-themes/pull/4032

• Some test images are missing borders, although these borders are visible in the browser (tested in Chrome and Firefox)
• The focus style of the row in fluent is currently not ideal. Needs to be checked and fixed.

Completed:

• [x] Move all grid variables to variables.scss files
• [x] Implement sm and md grid sizing options.
• [x] Add prefix $kendo- to grid variables
• [x] Use table classes in grid rendering
• [x] Unify table and grid sizing values
• [x] Create JSON structure
• [x] Docs article containing each mode.

Further actions required:

• [ ] Add sizing option for small grid and use table classes in jQuery
• [ ] Add sizing option for small grid and use table classes in MVC & Core
• [ ] Add sizing option for small grid and use table classes in Angular
• [ ] Add sizing option for small grid and use table classes in React
• [ ] Add sizing option for small grid and use table classes in Blazor
• [ ] Add sizing option for small grid and use table classes in Vue