Provide general provider-specific configuration in cloud profile about gardener-extension-provider-metal

[Gerrit91]

Proposal for cloud profile spec:

---
apiVersion: core.gardener.cloud/v1alpha1
kind: CloudProfile
metadata:
  name: metal
spec:
  type: metal
  providerConfig:
    apiVersion: metal.provider.extensions.gardener.cloud/v1alpha1
    kind: CloudProfileConfig
    iamconfig:
      groupConfig:
        namespaceMaxLength: 20
      idmConfig:
        idmtype: UX
      issuerConfig:
        clientId: auth-go-cli
        url: <dex-url>
    firewallImages:
      - firewall-1
    firewallNetworks:
      <partition-a>:
        internet: <partition-a-internet-network-id>
      <partition-b>:
        internet: <partition-b-internet-network-id>

[majst01]

merged into master