Previously, the global storage of these types either used a GHash or a
blender::Map. VectorSet is preferrable to GHash because it's type safe,
clearer, and faster. It's preferrable to Map because the key doesn't
have to be duplicated and because iteration is faster.
This PR moves these registered types to VectorSet, just like the
node, node socket, and node tree types. Note that none of these types
use RAII for allocation, so freeing is still done manually.
Testing was manually interacting with each of these systems, including
with addons that register their own types.
Pull Request: https://projects.blender.org/blender/blender/pulls/133778
ce5bdecf89