[TASK] Cleanup Localization Charset code

The protected property "AbstractXmlParser->charset" is set from
the outside but never used anymore in either the abstract class nor
in the subclasses.

The protected method "getCharset()" is basically useless:
a) it's never called or in use
b) it has nothing to do with the XmlParser as it does not work
with any properties / functionalities of the XmlParser itself.

The protected method "initialize()" is called solely in the
contructor which can be dealt with directly in the constructor
(that's what a constructor is there for).

The third parameter $charset within getParsedData() is
now not needed anymore within the Parsers, as all expect
UTF-8 for files.

Resolves: #80486
Releases: master
Change-Id: I929c3960fb5b94f5448a2d29f4a73fbb5d81a500
Reviewed-on: https://review.typo3.org/52185


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>