Tests emulation of the default locale.

Set locale to ru-RU
Detected locale: ru-RU
Date locale string: 02.04.2020, 20:02:00

Checking locale after navigation
Detected locale: ru-RU
Date locale string: 02.04.2020, 20:02:00

Checking locale after cross-origin navigation
Detected locale: ru-RU
Date locale string: 02.04.2020, 20:02:00

Set locale to zh-CN
Detected locale: zh-CN
Date locale string: 2020/4/2 20:02:00

Tried to set override from another session, got error:
Another locale override is already in effect

Reset locale to default
Default locale matches previous value: true

Tried setting bogus locale:
Invalid locale name