Add a capability to specify IPtags to public IP created as part of workload cluster

[jikuma]

/kind feature

Describe the solution you'd like
The workload clusters generated by CAPZ have a public ip for api-server. Azure, by default, assigns the IPs randomly.
We have a network-restricted SAW machine to access production resources. This Saw machine can access only the whitelisted public IP. Since these workload clusters get random public IP, these IPs are not part of whitelisted IPs; hence, these workload clusters cannot be accessed from the SAW machine.

One way to solve this issue is to specify IPtags while creating public ip. Each azure service is assigned an IPtag which is backed by a pool of public IPs. If we set the IP tags, Ips are assigned from the pool of already allocated public Ips. These IPs are whitelisted and hence can be accessed from the SAW machine.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:
Public

• cluster-api-provider-azure version: NA
• Kubernetes version: (use kubectl version): NA
• OS (e.g. from /etc/os-release): NA

[CecileRobertMichon]

/assign