DOC, TST: binary-exact deterministic renders

[tylerjereddy]

One thing that would be useful is to have some docs on deterministic rendering. The motivation should hopefully be obvious--if you can do deterministic renders you can do super useful things like regression testing with matplotlib.testing.compare.compare_images to a very high/binary exact tolerance for code bases that use MolecularNodes as a library. It would also mean that if you version control binary assets in a project that includes MolecularNodes renders, you don't have to keep seeing an image diff on i.e., small changes in light bounce "physics."

So, if this is possible (i.e., pinning Cycles random lighting seeds or something like that?), documenting it would be great. If it is not possible, or effectively considered unreasonable to expect, some brief docs indicating that would also help.