Add public DNS support to cluster-api-provider-azure for private clusters

[erkanerol]

User Story

As a user, I want to resolve DNS records for private clusters locally so that I can access endpoints after building a network connection to the cluster's VNET (e.g. via Azure VPN Gateway)

Details

CAPZ creates Public DNS Zone for public clusters and Private DNS Zone for private clusters. We want expose all records publicly but CAPZ doesn't support that.

We joined the upstream office hours and proposed this feature. They are OK if we open a PR. See the office hours notes https://docs.google.com/document/d/1P2FrRjuCZjGy0Yh72lwWCwmXekSEkqliUVTmJy_ETIk/edit#heading=h.as10066b77o8

Now, we create an additional public DNS zone with dns-operator-azure for private clusters and deploy 2 instances of external-dns.

Acceptance Criteria

• Add support to upstream CAPZ
• Remove related features from dns-operator-azure
• Update all MCs