Multi-Barcode + Multi-Resolution

DISCLAIMER: a note for downstream package maintainers: as discussed in #333 this release should have been named 2.0 not 1.3. Please don't package this release until the issue is resolved.

The major new features:

• Multi-barcode reading with the new std::vector<Result> ReadBardcodes(...) function. Does not work for Aztec, DataMatrix and Maxicode, yet.
• Multi-resolution scanning that can automatically downscale the input to substantially increase the detection rate on high resolution scans, see DecodeHints::tryDownscale, currently only enabled in the ReadBardcodes function
• New Result::symbologyIdentifier property (thanks to @gitlost)
• Updated and improved android wrapper (thanks to @markusfisch)

Worth mentioning:

• Most deprecated APIs from last release were removed (will likely break your build if you still have deprecation warnings with 1.2.0)
• New Result::lineCount and DecodeHints::minLineCount properties to improve reliability of 1D code reading
• New Result::isMirrored property (works for QRCode, PDF417, DataMatrix)
• Improved FNC1 handling and deprecation of DecodeHints::assumeGS1
• Lots of small fixes all over the place
• Drop in-tree copy of stb image library
• New OpenCV example code
• QRCode reading improvements
• Python 3.10 support

This includes around 200 commits including those of 11 new contributors.

Full Changelog: v1.2.0...v1.3.0