Refactored tzdb generation pipeline

[darrenldl]

Still some adjustment to be made

• Setting starting year to be 1990 may cause some time zones to have an empty table, as zdump would not output the transitions as the last transitions may be before 1990 (e.g. 1912)
  • We need the generator to be smarter and rerun zdump with another range if the output is empty

[darrenldl]

Added second try logic to generator, changed tzdb-full to only consider 1990 to 2040