Run godot --headless --import for 4.x

[menaechmi]

Godot puts class_names in the .godot folder (which is excluded from github upload). While you could upload the folder, it has the potential to contain sensitive information

Anyways the fix is just to run godot --headless --import once before running any tests, which will generate the folder for CI. Otherwise you'll get an error akin to

SCRIPT ERROR: Parse Error: Identifier "GutUtils" not declared in the current scope.
          at: GDScript::reload (res://addons/gut/gut_cmdln.gd:326)
ERROR: Failed to load script "res://addons/gut/gut_cmdln.gd" with error "Parse error".
   at: load (modules/gdscript/gdscript.cpp:2788)
Error: Process completed with exit code 1.

bitwes/Gut#589