pdl: Merge script/ and scripts/ subfolders

Rename the python parser to scripts/pdl/parser.py,
and the test file to tests/python_parser_test.py

Test: atest --host pdl_python_parser_test
(cherry picked from https://android-review.googlesource.com/q/commit:bb8c37924704a0ba9f9f993498d0ef55215bb6d4)
Merged-In: Ie32e9e384810bbc991e291e4863d37845f73c9b7
Change-Id: Ie32e9e384810bbc991e291e4863d37845f73c9b7