Add new callbacks for the new esilvm

i would go for just a single callback with a parameter to choose what to do. something like RAnalEsilCallback(RAnalEsil *esil, int type). this will reduce the size of the struct and ease the implementation. having too many callbacks is confusing and looks bloated to me. Also. I would prefer to have simpler lifecycle. like init/fini, to initialize the mem and hooks at once. for custom ops. they can be instantiated in the init callback. this is, when you select a plugin, it configures the new instructions setups the memory and hooks some points of the esil loop to handle arch-specific stuff. No need for having fine-grained callbacks here imho. Because i dont see why someone would need to instantiate an esil plugin without having the customops or not including the memory initialization stage. Also, in case of wanting to reset the state. it would be much simpler to just fini and fini the whole plugin at once.