Implement cached texture uploads utilizing `PF_State`

[Wunkolo]

Uses PF_State to conservatively upload the InputTexture only when needed. This optimizes the case where the source input layer is a static image, a time-remapped video, or a low-framerate image.

Ex, in the case of a static image, the source texture is only uploaded once, keeping track of its PF_State, and subsequent render requests will re-use this uploaded texture.

The coherency of PF_State needs to be validated a bit.

Resolves #5

[Wunkolo]

Red frames indicate a GPU upload of the input texture. With a 12.5 gif in a 50fps composition, the input-texture is now only uploaded to the GPU when the incoming frame index is unique from the previous.