Refactor existing android tz generation tools

Refactor existing android tz generation tools to enable the addition of
other, similar tools.

Also, switch to atest for the test code.

This commit contains small corrects to comments and a test fix.

Bug: 143451294
Test: atest tztools_common_tests
Test: atest tzlookup_generator_test
Change-Id: Ib1ca79afd711a8c7b133c8e85aba6ca6818905e5
11 files changed