Reorder the order the filelists are initialized per package.
Optimize speed of find_files_for_package:
  We can simply check if the modules entry is the same as last time.
  The code uses iterators instead of that C-ish for loops.
  Create a hash from the packagemodules to speed up the check if
  a module is included in the hash.

Change-Id: I1e8ae394634a527880e08ef8ff333d94d04f49fd
Before: 12s per language/package
After: <1s per language/package
Reviewed-on: https://gerrit.libreoffice.org/68339
Tested-by: Jenkins
Reviewed-by: Tomáš Chvátal <tchvatal@suse.cz>