Improve frame_generator sample tool (#9570)

- Add support for vector parameters (float2, float3, float4) in the 
  parameters file using `{x, y, z}` syntax.
- Allow comments (`#`, `//`) and empty lines in the parameters file.
- Make the end value optional in the parameters file 
  (defaults to start value).
- Add `--size` / `-S` option to specify viewport dimensions.
- Optimize rendering by pre-filtering active material parameters.
- Remove hardcoded default parameters and silently ignore missing 
  parameters to support shared configuration files.
- Add documentation for the parameters file format.

Author: pixelflinger