Create structs for ui objects in kueue-viz instead of ad-hoc objects

[akram]

What would you like to be cleaned:
In most backend functions, ad-hoc objects are created to convey data from the kube api to the websocket layer. This was done for several reasons:

• forwarding directly the kubernetes objects would have been too heavy as most of the fields are not used on the ui side
• the dashboard is, currently, a read-only view of aggregated data from the kubernetes api, so, it would not have been necessary to convey kubernetes data back for saving (for example)
• the sake of quick development

Why is this needed:
It could be interesting to have dedicated objects for this usage for better debuggability, especially on the client side, and to ensure data consistency.

As a first pass, we can create structs manually based on the existing ad-hoc objects. But, if we can find a way to generate them later it could be more efficient.

[akram]

/kind dashboard