Feat: Create namespace inline when adding a new provider

[valaparthvi]

When adding a new provider, Docker for e.g., the general pattern is to install it in a namespace called capd-system, or capa-system for an AWS provider. I find it slightly annoying to have to remember to create a namespace before adding a new provider. It might be interesting to create the namespace in-line while adding a new provider.

If the namespace entered does not exist in the dropdown, create one.

[mantis-toboggan-md]

We will likely need to do some work in rancher/dashboard to support this, it looks like that component expects to be in a cluster context, not global context like the CAPI ui https://github.com/rancher/dashboard/blob/master/shell/components/form/NameNsDescription.vue#L311