[4.4.dev 2] ufbx importer does not find Synty textures

### Tested versions

4.4.dev 2

### System information

Windows 11 Vulkan Forward +

### Issue description

I saw a similar report/post somewhere, but could not find it so I apologize if this is repeated somewhere.

The Synty assets that are released as their "Sources Files" contain .FBX files that reference links to Dropbox or the .psd image textures rather then the same file name with the .png extension that is actually contained in the files.

```
Resource file not found: res:// (expected type: Texture2D)
Can't open file from path 'res://Dropbox/SyntyStudios/PolygonHorrorMansion/_Working/_Textures/PolygonHorror_Texture_01.psd'.
modules/fbx/fbx_document.cpp:1088 - FBX: Image index '1' couldn't be loaded from path: res://Dropbox/SyntyStudios/PolygonHorrorMansion/_Working/_Textures/PolygonHorror_Texture_01.psd because there was no data to load. Skipping it.
Resource file not found: res:// (expected type: Texture2D)
Can't open file from path 'res://_Textures/PolygonHorror_Texture_01.psd'.
modules/fbx/fbx_document.cpp:1088 - FBX: Image index '0' couldn't be loaded from path: res://_Textures/PolygonHorror_Texture_01.psd because there was no data to load. Skipping it.
Resource file not found: res:// (expected type: Texture2D)
Can't open file from path 'res://PolygonShops/_Working/_Textures/PolygonShops_Walls_Texture_01.psd'.
modules/fbx/fbx_document.cpp:1088 - FBX: Image index '1' couldn't be loaded from path: res://PolygonShops/_Working/_Textures/PolygonShops_Walls_Texture_01.psd because there was no data to load. Skipping it.
Resource file not found: res:// (expected type: Texture2D)
Can't open file from path 'res://_Textures/Glass.psd'.
```
the ufbx importer does not appear, as a fallback, to look through the filesystem and find the matching filename with other extension types that can be used in place of the ones referenced that it is unable to find.

Additionally there appears to be no way to disable the ufbx importer so that the FBXState and FBXDocument classes can be used to override and "handle" the .fbx files.

### Steps to reproduce

I was importing .fbx files from their PolygonHorrorMansion Pack sourcefiles.

### Minimal reproduction project (MRP)

NA