nvencoder: Add support for RGB formats
Adding RGBA, BGRA, VUYA and RGB10A2_LE format support for performance. However, these formats are not still recommended if upstream can support native YUV formats (e.g., NV12, P010) since NVENC does not expose conversion related optiones. Note that VUYA format is 4:4:4 YUV format already but NVENC runtime will convert it to 4:2:0 format internally