Blender Git Loki

Depsgraph: Add query for whether graph is up to date

Depsgraph: Only invoke callbacks when there are changes

Only affects when an evaluated dependency graph is requested via
context.

Makes it cheap to call when there are no changes made to the graph

Transform: Ensure depsgraph is evaluated when needed

Fix based on D4455 from Campbell, utilizes some recently
introduced functions and allows to not have any extra checks
in the transform code.

Fixes T61904
Fixes T62135

Reviewers: brecht

Maniphest Tasks: T62135, T61904

Differential Revision: https://developer.blender.org/D4967