[!!!][TASK] Drop support for csConv recode

The recode option for $TYPO3_CONF_VARS[SYS][t3lib_cs_convMethod] is
removed from the Core.

There are better working, better supported and more stable
conversion PHP extensions (iconv, mbstring) available
which should be used instead.

Resolves: #72497
Releases: master
Change-Id: I98a681be35b67d1892c718cf6e1c51c55e0d480a
Reviewed-on: https://review.typo3.org/45533


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>