Snaps dependency issue during installation

[Soar Huang]

When building images with arguments (or via model assertion), order currently affect dependency
And some special cases would not follow the order

Case 1: (Order affect dependency)
If checkbox-shiner depends on checkbox20,
we must append "--snap checkbox20 --snap checkbox-vendor"
instead of "--snap checkbox-vendor --snap checkbox20" when building image.

Case 2: (Not follow the order)
Declare "default-provider: vendor-platform" in snapcraft.yaml of gadget snap, and declare "vendor-platform" before the gadget in the model assertion as well, always install gadget at first then building image failed due to the "default-provider"

error message is like as below:
error: cannot use snap "vendor-instrument-gadget" without its default content provider "vendor-platform" being added explicitly for all relevant modes (run, ephemeral)