Use dedicated enum ConfigurationKey instead int as function parameter

In qcanbusdevice.h, we have the following prototypes:

virtual void setConfigurationParameter(int key, const QVariant &value);
QVariant configurationParameter(int key) const;
QVector<int> configurationKeys() const; 

Was there a reason to use int for the key, and not the dedicated enum ConfigurationKey?

Do we want to change that for Qt 6?

If the enum is kept as-is (i.e. no enum class), it should be even source compatible with existing code.