Reduce rerenders of the entity component

[IdrissMahjoubi]

Recalculating all entities on each update is heavy work, thinking about this further, we don't really need to calculate them and store them in the plugin state. the main idea was to update them all, but we do that already without having to calculate all of them on each update.

Performance improvements:

• Only calculate unique entities
• Skip non-atom nodes in the search
• Prevent descending into entity nodes (since they can't have entity nodes content)
• unique entities are now only update if the actual unique entities change
• we compare the attributes to memoize the entities array instead of comparing using JSON.stringify

[ronnyroeller]

LGTM (pls see comment). Also, pls explain a bit further in the PR description why these changes help with performance. Esp removing the helper (which is an API change) would be good to explain why it's required (i.e. what's the benefit of it).
Reading through the code it seems to do sth with avoiding the positions, which allows for better caching (presumable because changing content around the entities doesn't impact the cached data any longer).