[BITV] Menus must be focus trapped

[PVince81]

Tabbing out of a menu should close it.

Need to check all the menus in the top bar:

• search: [stable25] Close global search menu when keyboard focus leaves #35233
• notifications: Close menu when focus leaves notifications#1367
• Popover component: check if they do (at least with Escape key)

Also: probably the menu should close when Escape is hit while inside the menu ? (need to check if WCAG requires this)

[Pytal]

Notifications nextcloud/notifications#1367

[Pytal]

@PVince81 @skjnldsv focus trap all header menus like in nextcloud-libraries/nextcloud-vue#3489 or allow tabbing out and closing like in https://github.com/nextcloud/server/pull/35090/files#diff-ae814dad42ef834e47dfd1d175e798e67c703ede5105470317fafabec5c2f60f

[skjnldsv]

I added focus trap on nextcloud-libraries/nextcloud-vue#3489 too to help with your ongoing accessibility work :)

[Pytal]

Roger, so since they are mutually exclusive then which one should we go for @skjnldsv @PVince81?