Cleanup: improve consistency between function node implementations

Cleanup: restore alphabetic ordering

Nodes: fix link drawing for some socket types

The type of sockets is `-1` in some cases, resulting in a crash
when accessing the `std_node_socket_colors` array.

Geometry Nodes: disable attribute search for non-attribute string sockets

This is a simplified version of D12730 by @erik85.

I added attribute search only to one legacy node for testing purposes.

Nodes: add utility to find NodeRef for node

In the future `NodeTreeRef` could have a lazy initialized map,
but for now this is good enough.

Geometry Nodes: fix force-computing multiple non-output sockets

There were some issues when multiple inputs of the same node
were forced to be computed (e.g. for the spreadsheet), but none
of the node outputs (if existant) were used. Essentially the node
was marked as "finished" too early in this case.

This fix is necessary for the improved viewer node (T92167).

Fix T92387: crash in legacy point distribute node

This was caused by rB40c3b8836b7a36303ea9c78b0932758cbf277f93.
The same fix exists in the Distribute Points on Faces node.

Cleanup: trailing whitespace

Fix: dangling pointer caused use-after-free

The old code only worked when built-in nodes are only unregistered
at most once while Blender is running. However, this is not the case
when running certain unit tests such as `AbstractHierarchy*`
in `blender_test`.

Found by Sybren, thanks.

Nodes: support sharing node declarations between nodes

Previously, every node had its own declaration. This isn't ideal, because
it's often the case that all nodes of the same type have the same declaration.
That's the case for all nodes using declarations currently. It will not be true
for e.g. group nodes in the future.

Sharing node declarations between nodes makes it a bit more efficient.

Differential Revision: https://developer.blender.org/D12898