Support using preloaded images with ml.net

[Cpt-Falcon]

Is your feature request related to a problem? Please describe.
The object recognition demo, for example, makes it impossible to import images in preloaded base64 format. Instead, I need to save files to disk, then pass the path so that the ML algorithm can consume them. I don't want to have to save to disk.

The specific static class is:

ImageEstimatorsCatalog

public static ImageLoadingEstimator LoadImages(this TransformsCatalog catalog, string outputColumnName, string imageFolder, string inputColumnName = null);

Describe the solution you'd like
Create an overloaded method that takes in an array of base64 strings instead of an image folder.

Describe alternatives you've considered
Write base64 image to disk, then pass paths to the pipeline

Additional context
Add any other context or screenshots about the feature request here.

[michaelgsharp]

@serp777 as a temporary workaround you could use a CustomMappingEstimator to convert the base64 string to a bitmap and then use the transformers we have built in from there on.