Updating grass canonical mapping and improved desaturation debug prints

[TheDuckCow]

With this, we now have correct prep material saturation again for this grass object, and all tests passing again.

Yes, this is intentionally a branch going into master, as I've already merged other work there. This should hopefully be the last change to merge for the 3.5.2 release.

Will let this sit overnight and review tomorrow with fresh eyes. Test results now:

-------------------------------------------------------------------------------
bversion   	ran_tests	ran	skips	failed	errors
-------------------------------------------------------------------------------
(3.6.2)   	all_tests	64	2	0	No errors
(4.0.2)   	all_tests	64	2	0	No errors
(3.5.1)   	all_tests	64	2	0	No errors
(3.4.0)   	all_tests	64	2	0	No errors
(3.3.1)   	all_tests	64	2	0	No errors
(3.2.1)   	all_tests	64	2	0	No errors
(3.1.0)   	all_tests	64	2	0	No errors
(3.0.0)   	all_tests	64	2	0	No errors
(2.93.0)   	all_tests	63	3	0	No errors
(2.90.1)   	all_tests	63	3	0	No errors
(2.80.75)   	all_tests	62	4	0	No errors