Use named options for verify_overlaps

Previously, verify_overlaps used positional arguments, the first was
the monolithi flags and the rest were the module flag pairs (filtered
flags file and signature patterns file). This change makes them use
named options to make the purpose of the arguments clearer on the
command line.

Bug: 194063708
Test: atest --host verify_overlaps_test
      m out/soong/hiddenapi/hiddenapi-flags.csv
Change-Id: Ife0af0016eb0f91416e8330d5d98cb53c97d68a4