Many ui features for geometry nodes need access to information generated
during evaluation:
* Node warnings.
* Attribute search.
* Viewer node.
* Socket inspection (not in master yet).
The way we logged the required information before had some disadvantages:
* Viewer node used a completely separate system from node warnings and
attribute search.
* Most of the context of logged information is lost when e.g. the same node
group is used multiple times.
* A global lock was needed every time something is logged.
This new implementation solves these problems:
* All four mentioned ui features use the same underlying logging system.
* All context information for logged values is kept intact.
* Every thread has its own local logger. The logged informatiton is combined
in the end.
Differential Revision: https://developer.blender.org/D11785
0153e99780