This change rearranges the testing dir structure to
be more hierarchical to enable a distinction between
test data and xTS test code.

The testing/ disto.zip files have been moved under
the output_data dir to match the structure found in
system/timezone.

This change also adds the oem_template directory that
can be used to bootstrap OEMs' own time zone data apps
and tests:

1) Moved the "demo" app files to be under under
oem_template/data_app.
2) Added an xTS test class / host library that can be used
in OEM-specific test suites by OEMs to make sure they have
integrated the time zone updates correctly.

Test: Manual
Test: make droid
Bug: 31008728

Change-Id: Ia4d4dc12647263acb4602cfcb1aa4f11026072f1