Blender Git Loki

Fix embedded IDs not being enough/properly initialized.

Among other things, they were missing library pointer, session uuid
initialization, etc.

Fix T74546: Corrupted nodegroups crash blender when copy pasting or
appending them.

Fix (unreported) asserts when undoing some production scenes (from
coffee run e.g.).

Initialy caused by rB0aac74f18f2d.