Some operations can take a lot of time to execute and
any duplication should be avoided.
This patch implements a compile step that detects
operations with the same type, inputs and parameters that
produce the same result and merge them. Now operations
can generate a hash that represents their output result. They only
need to implement `hash_output_params` and hash any parameter
that affects the output result.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D12341
b225a7c470