[AP] Set selected altitude

Set the selected altitude.

Set selected altitude value:
Coherent.call("AP_ALT_VAR_SET_ENGLISH", 1, Simplane.getAutoPilotDisplayedAltitudeLockValue(), forceNextAltitudeUpdateBool);

Enable selected altitude mode:
SimVar.SetSimVarValue("K:ALTITUDE_SLOT_INDEX_SET", "number", 1);