Tabs: use the _classes method.

Fixes #7053
Dialog: use the _classes method.

Deprecate dialogClass.

Fixes #7053
Accordion: use the _classes method.

Fixes #7053
Autocomplete: use the _classes method.

Fixes #7053
Slider: use the _classes method.

Fixes #7053
Spinner: use the _classes method.

Fixes #7053
Progressbar: use the _classes method.

Fixes #7053
Menu: use the _classes method.

Fixes #7053
Button: use the _classes method.

Fixes #7053
Tooltip: use the _classes method.

Fixes #7053
Selectmenu: use the _classes method.

Fixes #7053