EuiContextMenuItem needs to accept arbitrary components as children

[cjcenizal]

Based on use cases discovered in #250, we need to be able to support children such as:

• EuiSwitch
• EuiCheckbox
• EuiRadioGroup

In these cases, tabbing to an item should move focus to the first focusable child. As long as a child of the item retains focus, this item should retain the "focused state" blue background.

I don't think the item should be a focus trap. In other words, tabbing through a radio group and then beyond the last radio should move focus to the next EuiContextMenuItem.

CC @uboness

[chandlerprall]

Closing this issue. The design team is doing housekeeping against our issues and closing items without much recent activity. Feel free to reopen if you still have issues or feel this is in error.