Handle entity runner diffs cleanly

[lalalune]

Right now whenever anything changes (entity is marked dirty) we are attempting to destroy the entity and rebuild it... this is not happening cleanly though.

If the exact spell used by the entity is changed, we should destroy the old instance, create a new instance and attach it to the client. Ideally we don't need to destroy the client, but that might be easier. In either case we need to make sure that we aren't leaking memory or holding on to old references.

If the API key etc is changed, we'll need to completely destroy and restart that client. We want to keep the entity itself alive, but, for example, if we update Discord, we should destroy discord client and restart.

These services are meant to be long-running, so we should make sure they are starting and destroying properly and be meticulous about this.

[parzival418]

I was thinking about this with the new spell runner I am working on. In theory the spell runner could have a new spell loaded into it, or perhaps even just take on an OT diff and apply it to itself. This would reprocess the graph after the update, and should not interrupt the ability to run the spell itself. You could store all spells loaded in memory in a map or similar and just grab it and apply the update. I was thinking that is the next level up or architecture is whatever the spellRunner lives within.