Popover Menu: Toggle variant menu items cause accessibility error

[GCHQ-Developer-299]

Summary

While working on #1897 I found that we get a failing on our Popover story examples with 'toggle' variant menu items.

Accessibility Insights reports this button's existence as a failure, because interactive items should not be nested.

We need to modify our toggle variant menu items so that they don't cause issues for Accessibility Insights/Cypress (and still read okay to screenreaders like NVDA and VoiceOver)

Things that will need changing:

• [ ] Adjust ic-menu-item and/or ic-popover-menu so that the Toggle variant menu items don't break any rules.
• [ ] Popover cypress tests - once this issue is fixed we can re-enable A11y tests

💰 Use value

To meet WCAG 4.1.2

Additional info

Example of role=menuitemcheckbox working: https://www.w3.org/WAI/ARIA/apg/patterns/menubar/examples/menubar-editor/

Guidance on the menuitemcheckbox role: https://www.digitala11y.com/menuitemcheckbox-role/

[GCHQ-Developer-299]

This might require removing the ic-button from inside menu item, making sure that functionality/styling is maintained. Do before #2285