Previously when opening 2 images like `['img1.png' ,'img002.png']` the
sequence detection will open this images as a single image sequence.
However internally this is not a supported sequence.
To fix that this changes will also differentiate sequences
by their digit count, so if a group of images like:
`['img1.png','img2.png' ,'img002.png','img003.png']`
are open now it will create 2 images sequences instead of just one.
Ref: !120185
5c2d412a29