v6.x deprecations

[codemasher]

The following methods (property getters) have been deprecated in favor of asymmetric visibility, which is available as of PHP 8.4 and which is the minimum requirement of the next major version (v7) of php-qrcode.
The QRMatrix class will see an addition of a magic getter that emulates the future behaviour as an upgrade path, the other methods are only used internally and will see no such addition for the time being.

method	replacement
BitBuffer::getBuffer()	BitBuffer::$buffer
BitBuffer::getLength()	BitBuffer::$length
Detector::getFinderPatterns()	Detector::$finderPatterns
EccLevel::getLevel()	EccLevel::$level
ECICharset::getID()	ECICharset::$charsetID
FinderPattern::getCount()	FinderPattern::$count
GenericGFPoly::getCoefficients()	GenericGFPoly::$coefficients
LuminanceSourceInterface::getHeight()	LuminanceSourceInterface::$height
LuminanceSourceInterface::getWidth()	LuminanceSourceInterface::$width
LuminanceSourceInterface::getLuminances()	LuminanceSourceInterface::$luminances
MaskPattern::getPattern()	MaskPattern::$currentPattern
QRData::getBitBuffer()	QRData::$bitBuffer
QRMatrix::getEccLevel()	QRMatrix::$eccLevel
QRMatrix::getMaskPattern()	QRMatrix::$maskPattern
QRMatrix::getMatrix()	QRMatrix::$matrix
QRMatrix::getSize()	QRMatrix::$moduleCount
QRMatrix::getVersion()	QRMatrix::$version
ResultPoint::getEstimatedModuleSize()	ResultPoint::$estimatedModuleSize
ResultPoint::getX()	ResultPoint::$x
ResultPoint::getY()	ResultPoint::$y
Version::getVersionNumber()	Version::$versionNumber

The following properties as well as the method copyVars() in QROutputAbstract will be removed in v7 without replacement,
as they only existed to improve performance by circumventing the magic getters in the QROptions class - these are replaced by (set) property hooks where unnecessary overhead is reduced. Some of the built-in output classes may see the re-addition of some of these properties locally, depending on the performance impact.

QROutputAbstract::$excludeFromConnect
QROutputAbstract::$keepAsSquare
QROutputAbstract::$connectPaths
QROutputAbstract::$eol
QROutputAbstract::$drawCircularModules
QROutputAbstract::$drawLightModules
QROutputAbstract::$circleRadius

These changes are already in dev-main.