[Bug] Prompts are dismissed when putting the app in background but recreated if "Don't keep activities" is enabled

[Mugurell]

Steps to reproduce

• Access https://www.456bereastreet.com/lab/html5-input-types/
• Tap on a an element that would trigger a prompt to show

"Don't keep activities" disabled	"Don't keep activities" enabled
Keep.mp4	DontKeep.mp4

Expected behavior

In both cases (with / without "Don't keep activities") the prompts should behave the same.
Not sure whether they should be shown until the user explicitly consumes them or not.
On Chrome prompts remain on the screen until explicitly consumed but are not recreated if the Activity was killed in the background (mirrors Fenix's behavior).

┆Issue is synchronized with this Jira Task

[stale]

See: #17373 This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.