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

- Use a string instead of a frozenset to define _category_cf. The string
  form will fit into `invisible_regex` constructor more easily.
- Update the the characters using Python 3.7's unicodedata v11.0.0.
  Seven new characters were added: {'\U0001bca3', '\U0001bca1',
  '\U000110cd', '\u0605', '\U0001bca2', '\U0001bca0', '\u08e2'}
- Rewrite invisible_regex using _category_cf and re.compile.

Change-Id: I5adf1d1d9b714ec00bbd8854d36b3253d01824d7

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