This patch refactors the instance component to make use of the earlier
refactoring in rB4599cea15dcf. Now we don't have to build an array of
instance references the size of the point domain, and we can gather the
possible instances only once and use the same vector for all component
types. Generally the node should be a bit faster and use less memory.
The logic is moved around a bit, especially the hashing of the ID
attribute to pick from the instance list, but the result is unchanged.
Differential Revision: https://developer.blender.org/D11203
9569a522f2