The `Styles` option contains styles which are unsupported in
emails. The few that are supported can be replaced by other options.
- Shadows: unsupported;
- Rounded rectangle: (unsupported in Outlook)
is replaced by the `Border` options which allows to customize the
border's radius more than the current option.
- Thumbnail: can be done with a combination of `Border` and `Padding`
- Circle: can be done with a shape
(which has been added along with other new shapes)
This option could be found on images and icons and has now been removed.
CSS styles in the `theme_default` file have also been removed since
they are no longer needed.
Three basic shapes (circle, triangle, "slanted" rectangle) have been
added to the `web_editor`'s `Basics` shapes page.
A condition was previously set on the page to avoid showing an empty
page. The condition is moved to each of its buttons instead, so that
new shapes added via xpath from `mass_mailing` to this page are now
visible.
task-2836942
Part-of: odoo/odoo#95974
