Changes and new features:
1. Introduce new CRD `ProviderNetwork` for underlay/vlan networking management;
2. Specify provider inetrface on nodes in provider network;
4. Exclude nodes in provider network;
5. Link local IPv6 address and route will NOT be transferred to OVS bridge;
6. Builtin hybrid network support - create/update/delete underlay/vlan networks dynamically;
7. Set MTU of Pod interface to provider interface's MTU on each node;
8. Add new fields in CRD `Vlan`.

Gateway node(s) forward egress traffic to external gateway based on
policy routing. Support both distributed and centralized gateway modes.
New properties are available in subnet spec: externalGateway,
policyRoutingPriority & policyRoutingTableID.

Signed-off-by: Wan Junjie <wanjunjie@bytedance.com>

fix building error

fix: check error vaule

feat: vpc nat gateway

feat: vpc nat gateway

feat: vpc nat gateway

Co-authored-by: feixiang43 <352447595@qq.com>

This patch allow kube-ovn-controller combine multus-cni to allocate addresses for subnet providers other than ovn by annotate pods with allocated addresses. Users need to create subnet CRs and set the provider with <name>.<namespace> of NetworkAttachmentDefinition defined by multus-cni. Then kube-ovn-controller will combine the `k8s.v1.cni.cncf.io/networks` annotation and address information in subnet cr to determine an address.

This patch only implement the controller side logical, we need other patches to complete the cni part that communicates to apiserver and fetch the address information to the main cni.