Build the active filter chain only when its configuration changes,
including filter settings or order, input format, dimensions, output
size, and DMA mode.
Unchanged frames now execute only the cached active filters, avoiding
repeated setup, preparation, and output-resolution queries.
Reconfiguration forces a full-frame pass to prevent stale intermediate
framebuffer contents.
Also refresh CAS and FSR uniforms when loading presets and move
downscale pass selection out of the per-frame path.
According to Erik @ NVidia the open source NVidia driver will not
create a EGLImage from a DMABUF if the target is not
GL_TEXTURE_EXTERNAL_OES. This change set converts the dmabuf texture
from GL_TEXTURE_2D to GL_TEXTURE_EXTERNAL_OES and at runtime performs a
global search & replace on fragment shaders as needed to remain
compatible, replacing `sampler2D` with `samplerExternalOES`.
Ref: https://github.com/NVIDIA/open-gpu-kernel-modules/discussions/243#discussioncomment-3283415
This saves a lot of GPU power for partial updates. Running testufo with
lanczos downscaling and FSR upscaling consumed over 90 W, but with this
commit, consumed only 75 W.
