Multi-cluster support in loxilb

[UltraInstinct14]

Based on community discussion, following has been agreed upon as initial multi-cluster support feature :

1. There will be multiple kube-loxilb instances for different clusters
2. Each kube-loxilb should be able to allocate unique VIPs from a whole cluster perspective
3. Currently each kube-loxilb has CIDR declaration in its yaml and allocates VIP independently
4. But for multi-cluster scheme, CIDR allocation should be moved to loxilb
5. Also, considering current users are used to CIDR per kube-loxilb yaml , so current behavior should be preserved for backwards compatibility. Probably if no CIDR is specified, then only use loxilb IPAM. ( But it will be implementation specific how to ensure backward compatibility)

[gcezaralmeida]

Looking forward to this.