Add Image support to the new In-Memory File Storage capability

[jordimontana82]

Starting with FXE versions 2.6 / 3.6, a new In-Memory file database has been added. Check the docs for more info: https://dynamicsvalue.github.io/fake-xrm-easy-docs/quickstart/file-storage/

However, Image type support was descoped in orde to give priority to other fixes. This issue will keep track of what's necessary to bring Image type support.

https://learn.microsoft.com/en-us/power-apps/developer/data-platform/image-column-data?tabs=sdk#image-file-types

Same messages for Upload / Download can be used for images, with the below considerations

• Images: DeleteFile is not supported for Images
• InitializeDownload and DownloadBlock will fail if the ImageAttributeMetadata has CanStoreFullImage to false (only supported if True)
• Images: When retrieving Image data via .Retrieve, only the thumbnail is retrieved, the full image needs a separate download.
• Images won't be retrieved if ColumnSet.All is used, they need to be queried explicitly.
• Only one PrimaryImage can be set on create at the same time.
• Images: If CanStoreFullImage in metadata is set to true when uploading images, then images are stored like normal files.
• Images: with files, any file extension that is not blocked it's allowed, but with Images, only these file formats are supported: gif, jpeg, tiff, bmp, & png (fixed list not configurable via Organization)

Images: Special behaviour, columns have extra added internal columns: imageId, URL, and timestamp.

• Make the assumption the imageId is the fileId
• Timestamp will be generated automatically on add / update
• URL is relative url with the following format:

/Image/download.aspx?Entity=<entity logical name>&Attribute=<image column logical name>&Id=<image id value>&Timestamp=<time stamp value>