Blender shows invalid links in red in the node editor. However, it's not always
obvious why some links don't work, especially for beginners. This patch adds
additional information for every invalid link on the node that it links to.
The following error messages are added:
* Invalid link because of missing implicit conversions.
* Link cycle in node tree.
* A link from a field to a socket that does not support fields.
* Using the same menu on multiple Menu Switch nodes.
Currently, there are some per tree-type special cases in the link validation code.
In the future, this should be moved to tree type specific callbacks.
Pull Request: https://projects.blender.org/blender/blender/pulls/121976
399f6a1c60