Revert "pywikibot.tools.chars: Update and simplify the code"
Revert "pywikibot.tools.chars: Update and simplify the code"

Revert 02e3830b5826, but keep added characters.

Replace `_invisible_chars = frozenset(_category_cf)` with
`_invisible_chars = _category_cf`, _category_cf is already a frozenset
and there is no need to create a copy of it.

Bug: T202238
Change-Id: Ie55d3ba5f100e691f901f6be15e61425aef70795

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