Replace ImagePixelExtractingEstimator values at runtime

**Is your feature request related to a problem? Please describe.**
I am using orderOfExtraction: ImagePixelExtractingEstimator.ColorsOrder for ONNX pipeline. However, I need to select exact values for this attribute like:: orderOfExtraction: ImagePixelExtractingEstimator.ColorsOrder.ARBG. There are 6 options to select from (ARGB, ARBG, ABRG, ABGR, AGRB, AGBR). Instead of hardcoding these attribute values I need to pass a variable at runtime for these.

**Describe the solution you'd like**
For ONNX orderOfExtraction: ImagePixelExtractingEstimator.ColorsOrder.ARBG, there are 6 options to select from (ARGB, ARBG, ABRG, ABGR, AGRB, AGBR). Instead of hardcoding these attribute values I need to pass a variable at runtime for these.

**Describe alternatives you've considered**
I tried to replace this value as variable, but I am not sure how can I use variable in place of this attribute value.

**Additional context**
var pipeline = mlContext.Transforms.ResizeImages(resizing: ImageResizingEstimator.ResizingKind.Fill, outputColumnName: "data", imageWidth: ImageSettings.imageWidth, imageHeight: ImageSettings.imageHeight, inputColumnName: nameof(ImageInput.Image))
.Append(mlContext.Transforms.ExtractPixels(outputColumnName: "data", orderOfExtraction: ImagePixelExtractingEstimator.ColorsOrder.AGRB))
.Append(mlContext.Transforms.ApplyOnnxModel(modelFile: modeltoInfer.ModelPath, outputColumnName: "model_outputs0", inputColumnName: "data", gpuDeviceId: gpuDeviceId, fallbackToCpu: fallbackToCpu));