Make asset loading no longer use the type of the load.

[andriyDev]

Objective

Fix a bunch of weird edge cases of asset loading:

• Currently when loading an asset, we use the type of the handle to decide which loader to use, and if that is ambiguous, we fall back to using the extension.
  • So for example, if we call asset_server.load<Gltf>("whatever.png"), this will try to use the GltfLoader since we prioritize the asset type not the extension.
• We're able to load the same asset path multiple times provided that you use different asset types.
  • For example, if you call asset_server.load<Image>("whatever.png") and asset_server.load<Gltf>("whatever.png"), this will actually do two loads, even though one of these loads makes no sense!
• Untyped loads can't be deduped.
  • Even if we see a load happening for a specific path, we don't know whether that load is the right type, so we have to fully do the load just to then find out that the type of the asset we loaded was wrong.

Solution

• We no longer pass the type when finding the loader. This significantly simplifies the loader selection.
• This means that loading a path is now totally unambiguous allowing for future simplificaftions.

I haven't fixed all of the above issues, but this is the first step.

Testing

• None. This is pretty much a delete.