Adds a new overlay called "Timings" to the Geometry Node editor.
This shows the node execution time in milliseconds above the node.
For group nodes and frames, the total time for all nodes inside
(recursively) is shown. Group output node shows the node tree total.
The code is prepared for easily adding new rows of information
to the box above the node in the future.
Differential Revision: https://developer.blender.org/D13256
e4986f92f3