Make MTLContext more extendable

I want to create a texture from a CGImage. Great, MTLContext has a method for that:

Lines 75 to 78 in 56c46ca

    
           public func texture(from image: CGImage, 
        
                               srgb: Bool? = nil, 
        
                               usage: MTLTextureUsage = [.shaderRead], 
        
                               generateMipmaps: Bool = false) throws -> MTLTexture {

But I want to specify custom storageMode, which the current function doesn't support. Okay, so I'll make an extension on MTLContext to add this functionality. Unfortunately, that is not possible because MTKTextureLoader being private on MTLContext. Now I'm forced to create my own MTKTextureLoader alongside my already existing MTLContext and get less of the benefit of using MTLContext in the first place.

Maybe it's a small thing, but it would be nice if MTLContext could be optimized for extendability by making its MTKTextureLoader public. What do you think?

Honestly I just didn’t know MTKTextureLoader allows to customize storage mode, if it does, the it is basically a bug that MTLContext does not have this argument in this method

Oh yeah I just checked and it really does provide this option. For some reason I was sure MTKTextureLoader only supports shared storage.

I think we should add all proxy methods of MTKTextureLoader to MTLContext, like we did with MTLDevice and MTLCommandQueue. @eugenebokhan what do you think?

In regards of making it public, I think we can do that too also?

@s1ddok I like the idea, its going to be consistent with our current approach. Maybe I'll do the corresponding PR soon.

@OskarGroth I've addressed this in latest release (0.16.2), by making texture loader public. We will proceed with the API additions shortly. Thanks for raising the issue!

	public func texture(from image: CGImage,
	srgb: Bool? = nil,
	usage: MTLTextureUsage = [.shaderRead],
	generateMipmaps: Bool = false) throws -> MTLTexture {