Cluster Templates don't remember advanced settings in edit wizard

### What happened

One of our customers reported this issue and I can easily reproduce it. This is what I configured during the creation of the cluster template:

Now when I edit that cluster template, this is what I see instead:

It seems to remember that a provider preset was used (since that field is disabled) but doesn't show which. It also doesn't use it to fetch the data from OpenStack, as it tells us to provide credentials first. I can enable the preset field by clicking on the "Application Credentials" button, but even after choosing the same preset again, the advanced settings remain empty (except for the Floating IP Pool, which probably just displays the default instead - which is kinda worse tbh).

To be clear, the ClusterTemplate resource does contain the information, it's just an issue with filling them into the form.

```
$ k get clustertemplates czz6vwgbxw -o yaml | yq .spec.cloud.openstack
credentialsReference:
name: credential-openstack-czz6vwgbxw
namespace: kubermatic
floatingIPPool: public
network: CARE
nodePortsAllowedIPRanges:
cidrBlocks: []
routerID: ""
securityGroups: kubernetes-v1
subnetID: c232d8bc-a4cb-4494-8e7e-b3b8e6c87bce
```

I'm pretty sure this used to work, although I can't say when I last saw it working.

### Expected behavior

The wizard to edit cluster templates loads/shows/uses all the correct values from the cluster template.

### How to reproduce

- Create cluster template, presumably using a provider preset (but I didn't test other ways to provide credentials) and specify custom sec group / network / subnet
- Edit the same cluster template and notice your settings are not shown

### Environment
- UI Version: v2.29.2
- API Version: v2.29.2
- Domain:
- Others:

### Current workaround

Fill out everything again, if you remember (since the customer can't access the YAML)

### Affected user persona

End User

### Business goal to be improved

### Metric to be improved

Start at the cluster-template edit wizard and trace how the ClusterTemplate spec.cloud.openstack values are mapped into its form. Compare the stored credentialsReference, floatingIPPool, network, securityGroups, subnetID, and routerID with the fields shown during editing; done means the wizard displays and uses the saved values.

Written by the indexing model from the issue text.