Remove reuse of TimeZoneDistro

TimeZoneDistro is becoming single-use to better reflect its
normal usage as a wrapper around a stream from a
ParcelFileDescriptor.

This change switches to using methods on TimeZoneDistroBuilder
that return byte[] instead of TimeZoneDistro objects. Returning
TimeZoneDistro objects from TimeZoneDistroBuilder will be removed
in future changes.

Bug: 31008728
Test: make cts
Test: run cts -m CtsLibcoreTestCases -t libcore.tzdata.update2.TimeZoneDistroInstallerTest
Change-Id: I85d1854dacc5e3637020010d40abf3199a0fd3bb