Blender Git Loki

User Interface: Remove the green background when inside a node group

The current background color and parent nodetrees is too distracting and noisy.
It drastically affect the readability of the nested node-trees.

Other techniques (better bread crumbs) can be used instead to indicate
to users that they are inside a node group.

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The background drawing was introduced in 4638e5f99a9ba as part of the
Python Nodes branch merge. This made its debut in Blender 2.67
(30/May/2021).

At the time the color used for the background was a light gray. Over the
years the color changed to the current dark green, aggravating the
problem further.

Before that, the (expanded) nodegroup already had the partially
transparent background, mingling with the other nodes. The Python Nodes
branch brought this concept with its changes, and would always draw up
to two levels up in the background (the parent nodetree, and its parent
nodetree).

To read the original inspiration for all the changes introduced then:
https://code.blender.org/2012/01/improving-node-group-interface-editing/

Differential Revision: https://developer.blender.org/D12780