Consider equivalent time zone IDs as equal in metrics.

Maps equivalent time zone IDs(like America/Nuuk and
America/Godthab) to the same number.
Zones like Europe/Moscow and Europe/Volgograd are
treated as different even though they are identical starting
from the end of 2020 and users won't notice any difference.

Bug: 172934905
Test: atest com.android.server.timezonedetector
Change-Id: Id0b82a98f0fc6bd9edf63280e316c15d540f15ae