Improve image upload thumbnail generation failure

[ssddanbrown]

Right now massive images can be uploaded but they can fail resizing due to hitting memory limits.
Currently, the original image will remain and cause load failure of the image gallery as it attempts to re-create the thumbnail.
We should:

• Not allow thumbnail generation to cause the image gallery load to fail.
• When an image is uploaded with thumbnail error, the image upload action should fail with better error message and the original image should not remain in the system. (Flat out fail to avoid keeping an image that we can't handle and may not be suitable for content).

Opened after discussions in #2920.

[ssddanbrown]

Closed via #4578