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 private 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 private 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

All modified and coverable lines are covered by tests ✅

Project coverage is 52.95%. Comparing base (2acf550) to head (14ce92f).
Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5666      +/-   ##
==========================================
+ Coverage   52.83%   52.95%   +0.11%     
==========================================
  Files         278      279       +1     
  Lines       29610    29634      +24     
==========================================
+ Hits        15645    15692      +47     
+ Misses      13148    13123      -25     
- Partials      817      819       +2     

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[willie-yao]

/ok-to-test

[willie-yao]

/retest

@sadasu Can you please run make generate to fix the verify error?

[willie-yao]

/retest

[sadasu]

@willie-yao could you please take another look? Thanks!

[jhixson74]

LGTM, I don't have anything to add here.

[nrb]

I don't think this comment is correct