Detect and remove duplicate textures in level assets

[Zemanzo]

Description
Currently when uploading models, each model gets stored separately. If a two models have an identical texture, it is not shared, but instead saved twice. This creates unnecessary bloat in the level files, and causes the client to load the level slower due to a higher file size.
To solve this, it would be good to detect duplicate textures in models. The texture will be saved once, and inside the models there will only be a reference to this texture.

Minimum Acceptance Criteria

• During export in the editor, detect duplicate textures and reduce it to a single texture in the exported file.
• Support loading levels that have models with textures as a reference (in both client and editor).

Related issues
#262 should be taken into consideration when working on this issue