fedora: allow disabling weak dependencies

[supakeen]

Weak dependency resolution is hardcoded per imagetype. This commit changes it so weak dependency resolution can be turned off per image.

We guard on the Fedora version to ensure we don't accidentally change older images.

This commit also disables weak dependency resolution for Fedora Minimal which I have mentioned here.

[schuellerf]

The inverted logic is necessary for "backwards compatibility" or just to map the default behavior better? I.e. disableWeakDeps=false is actually weakDeps=true

[supakeen]

The inverted logic is necessary for "backwards compatibility" or just to map the default behavior better? I.e. disableWeakDeps=false is actually weakDeps=true

I did it because the imageType struct has no constructor and the default value for a boolean is false. It also maps pretty well on the behavior I'd like; fetch weak deps by default but explicitly disallow them per-image :)

[supakeen]

I'll be moving this to draft so it can be rewritten to use image config(s) as per @thozza / @achilleas-k 's request.