Move inner class WallTime from ZoneInfoData

ZoneInfoData itself does not depend on WallTime / TimeZone / Calendar
classes. The package import java.util.TimeZone makes it harder to
spot runtime cycles, because TimeZone depends on ZoneInfoData.
Thus, removing the package import and moving out WallTime to improve
the readability of dependencies.

Bug: 139480281
Test: CtsLibcoreTestCases
Change-Id: I7742400aae19e187d9fb0eeee7b0e48defd9c02f
4 files changed