Don't recreate default node groups

[BrendanParmer]

As Blender builds up its library of default node groups, there's been a growing need for NTP to not recreate these special node groups. It would be best not to recreate these groups when safe and possible

[BrendanParmer]

Probably not enough time for this to make it into NTP v4.0, but maybe afterwards

[BrendanParmer]

Playing around in Blender 5.0, definitely think this'll need to go in NTP v4.0. These essentials node groups are too common/useful, and things get hard to maintain when recreating these groups