RenderReport: Add option to add platform specific overrides.

Reference images in the reference_override_dir will be chosen before
images in reference_dir. This allows platform specific reference
images, with a common base.

Ignored when set to None. The caller is responsible
of setting the reference override dir as the unit test is more aware
what the definition of a platform is.

Patch adds `gpu.platform.device_type_get` function to get the device
type that blender has detected.

Reviewed By: brecht

Maniphest Tasks: T99046

Differential Revision: https://developer.blender.org/D15265

tests/python/gpu_info.py

@@ -0,0 +1,24 @@
+"""
+    Prints GPU backend information to the console and exits.
+
+    Use this script as `blender --background --python gpu_info.py`.
+"""
+import bpy
+import gpu
+import sys
+
+# Render with workbench to initialize the GPU backend otherwise it would fail when running in 
+# background mode as the GPU backend won't be initialized.
+scene = bpy.context.scene
+scene.render.resolution_x = 1
+scene.render.resolution_y = 1
+scene.render.engine = "BLENDER_WORKBENCH"
+bpy.ops.render.render(animation=False, write_still=False)
+
+
+print('GPU_VENDOR:' + gpu.platform.vendor_get())
+print('GPU_RENDERER:' + gpu.platform.renderer_get())
+print('GPU_VERSION:' + gpu.platform.version_get())
+print('GPU_DEVICE_TYPE:' + gpu.platform.device_type_get())
+
+sys.exit(0)