Add ability to disable creation of dns zone for unmanaged installs

[sadasu]

Similar to managed installs, add ability to optionally create DNS zones for unmanged installs.

What type of PR is this?
/kind feature

What this PR does / why we need it:
This PR adds the ability to optionally create DNS zones for unmanaged clusters. Without this feature they are always created. There are some instances we would like to use a DNS service other than Azure DNS and would like CAPI to withhold creation of DNS Zones at those times. This feature adds a new field to NetworkSpec that allows us to skip creation of the DNS zone. Default behavior remains unchanged where DNS zones are created during cluster creation.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

Add ability to optionally create the Private DNS Zone for unmanaged clusters instead of always creating one. Setting `PrivateDNSZone` within the `NetworkSpec` to `PrivateDNSZoneiCreationModeNone` will skip creating the Private DNS zone.

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @sadasu. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 53.19%. Comparing base (3625700) to head (1ed0e07).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
azure/scope/cluster.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5666   +/-   ##
=======================================
  Coverage   53.18%   53.19%           
=======================================
  Files         272      272           
  Lines       29582    29582           
=======================================
+ Hits        15733    15735    +2     
+ Misses      13029    13027    -2     
  Partials      820      820           

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[willie-yao]

/ok-to-test

[k8s-ci-robot]

@sadasu: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-provider-azure-verify	1ed0e07	link	true	/test pull-cluster-api-provider-azure-verify
pull-cluster-api-provider-azure-apiversion-upgrade	1ed0e07	link	true	/test pull-cluster-api-provider-azure-apiversion-upgrade

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.