Fix shading on CNC shape models

[Montandalar]

Luanti 5.11 showed a lot of flaws in the shading of the CNC models, some of which were previously obscured. Fix the models so that smooth shading is applied where appropriate and sharp/flat shading where appropriate. The modified files have also been run through ExeVirus' CompressObj.

This PR cherry-pick of minetest-mods/technic#661 done for your convenience. Please see that PR for the spreadsheet with rationales and the before/after screenshot.

[Montandalar]

Mineunit failing but I didn't change the code at all...

[BuckarooBanzay]

lgtm

[S-S-X]

Mineunit failing but I didn't change the code at all...

Two failing tests are for #400 and #399 and were failing before this one, so not caused by this PR.

241 successes / 2 failures / 0 errors / 4 pending

Failure → spec/api_spec.lua @ 42
Technic API Machine registration registers my_mod:my_solar_array
spec/api_spec.lua:86: Expected objects to be equal.
Passed in:
(table: 0x7fb5652e8650) { }
Expected:
(table: 0x7fb5652e8060) { }

Failure → spec/other_spec.lua @ 45
Coal alloy furnace wont crash without placement callbacks
spec/other_spec.lua:48: Expected no error, but caught:
(string) 'bad argument #1 to 'ipairs' (table expected, got nil)'