[context-menu] Implement accessible disabled menu items with tooltip support

[web-padawan]

Describe your motivation

Same as #4585 but for the following components:

• vaadin-context-menu-item
• vaadin-menu-bar-item

Main use case is to be able to show a tooltip explaining why some element is disabled.

• Disabled menu items can be focused
• Disabled menu items can be hovered
• Tooltips supported in disabled state

Describe the solution you'd like

Implement "accessible disabled items" feature. Prototype branches:

• https://github.com/vaadin/web-components/compare/proto/accessible-disabled-menu-items
• https://github.com/vaadin/web-components/compare/proto/menu-item-tooltips

Describe alternatives you've considered

Not using pointer-events: none - this was was done in base styles but reverted in #10413.

Additional context

Total estimate based on the discussion in private repo: 2 days (basics) + 5 days (tooltips) = 7 days.