Stacking filters

First, thank you for this great library.

Context. I'm building a flutter application and looking to provide some basic video processing capabilities to users. Currently, I am experimenting with applying different filters simultaneously on the video, for instance, applying a blur and a negative.

On iOS, I was able to get this to work relatively easily, since you can apply a filter on the result of a previous transformation.

With litr this doesn't seem possible. If you use multiple VideoFrameRenderFilters, they override each other rather than stack. I'm fairly new to Android / video processing so I might be missing something.

@izzytwosheds Do you perhaps know if this is already possible? Or would the only way to apply such an effect require writing a compound VideoFrameRenderFilter?

Start by tracing how VideoFrameRenderFilter instances are applied in LiTr’s Android/Java pipeline; the issue names no source file or test. Determine whether filters can be composed instead of overriding one another, with support for applying blur and negative together marking the desired outcome.