`CastingImage#userData` causes a lot of lag

[Real-Luxof]

Describe the feature

CastingImage#userData is a CompoundTag which means that anything and everything put into it is eagerly serialized and then has to be deserialized later when recalled. This makes hexes that put a lot of data in the Ravenmind extremely laggy (such as a simple veinminer hex), with the lag dropping like a rock if only the stack is used.

Using a custom implementation HashMap<String, Object> with a private put(String, Object) method and a public put(String, NbtElement) along with all the neat TagCompound methods instead of an actual TagCompound would solve both the issue of "everything must be serializable" and the issue of the lag.

Additional context

For addons that would want to store weird data types anyway, a TagSerializable interface that can also go right in might be nice to have.