Metadata trait should return guaranteed Metadata

[clux]

we know if it's there or not.
oversight from last release. upstream also does not do this.

That said, it is possible that we need to do a default deserialize if it ever is missing though.. we kind of do that some places in kube, but only for ListMeta: https://github.com/kube-rs/kube/blob/a6060c47e28dc82355efafa7f00e547fad4038a0/kube-core/src/object.rs#L25-L26

It'd be a bit annoying to not know if .medata exists, but it's technically +optional in the schemas: Pod or newer Eviction...

Going to try to NOT do this first.

[Danil-Grigorev]

My feeling is that this +optional is very much not (2015 is very early), and it is best to default the ObjectMeta to an empty content, then to introduce a breaking change in traits of kube-rs. Unrelated discussion, taken out of context upstream revolve around that “metadata is not enough” (meaning they need a superset of it, not something else).