Implement CopyTextureToTexture

[AlexAPPi]

In the engine, there is a copyRenderTarget mechanism, but there is no function for copying one texture to another while specifying mipLevels. It would be great to have such a feature.

https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/copyTexSubImage2D
https://developer.mozilla.org/en-US/docs/Web/API/GPUCommandEncoder/copyTextureToTexture

[mvaligursky]

indirectly related (Texture API) #4290