Port shader effect property connection optimization to QQuickGenericShaderEffect

Commit 8c745d808527684836d04da9014ee33c7cf8b6f1 contains multiple optimizations for QQuickOpenGLShaderEffect:

• Don't use a signal mapper, but handle the mapping using a custom slot object and a lambda to do the dispatching ourselves.
• Don't do meta-calls by property name, but by index.
• Cache the meta-object.
• Resolve the property indices by using the QML property cache.

These need to be ported to QQuickGenericShaderEffect.