zxing-cpp: update to 2.0.0.

The most visible change from the client perspective is the removal
of all formerly deprecated API, (almost) completing the 'cleanup'.
Since I was way too slow with this release to implement a 'cleanish'
SemVer release as discussed in #333, I decided to release this 2.0
with SONAME 3. A 3.0 release might bring the major version number
back in sync with the SONAME.

Major Changes

    switch to UTF8 based API and remove deprecated UTF16 one (Result::text())
    remove all API deprecated in 1.4
    Adding a wrapper for iOS by @parallaxe in #337
    new Aztec detector implementation to support arbitrary rotation and position of the symbol
    support multi-symbol detection in Aztec detector
    replace all Qt originated ECI/CharacterSet conversion code with a new implementation provided by @gitlost (libzueci)
    require c++17 to build library and client code
    new DecodeHints::textMode() and Result::text(TextMode) API to specify how bytes are rendered into text.
    HRI (human readable interpretation) is the new default for the TextMode (has been for most cases before, but not all)
    new DecodeHits::tryInvert() feature to test for inverted symbols (white on black background)

Minor Changes

    deprecate TextUtfEncoding helpers, not required anymore with UTF8 APIs for both reader and writer
    support for multi-symbol and arbitrary position detection of DataMatrix symbols when library is built with c++20
    Include version number of QR Code and DataMatrix in Result by @markusfisch in #396
    reduce size of Result struct by about a third
    cleanup all license related files (see removal of the Qt code above)
    update links and comments to refer to new github.com/zxing-cpp/zxing-cpp home
    improved Code128 decoder for over/underexposed images
    support python 3.11
    a whole bunch of fixes and minor improvements all over the place


(wiz)