[tests] Allow multiple options for script_tests.py
[tests] Allow multiple options for script_tests.py

Currently we only use "-help" and "-simulate" options for script tests.
But we also could do more tests e.g. with generators like
"-simulate -page:Main Page" in future. Therefore the TestScriptMeta
must accept an option string with more than one option.

Change-Id: I717118a0b55b813b4ac2574af72ceb177241ecc1

PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core