💎 refactor most services into Reconcile/Delete pattern

[CecileRobertMichon]

What this PR does / why we need it: Remove the exported Get() function from every Service except availability zones, virtual machines, scale sets, and managed clusters (these will be addressed in follow-ups.)

In order to keep the size of this PR manageable and facilitate reviews, I tried to scope this refactor down to only Services that did have Get() calls within the controller/reconciler.

** ⚠️ Important:** This is NOT the north star. This is closer to the end goal:
https://github.com/CecileRobertMichon/cluster-api-provider-azure/compare/reconcile-delete...CecileRobertMichon:public-ips-scope?expand=1#diff-890b2d661da1708cb3d23d43fc548ceeR28
This PR is just an intermediary step to get there.

Future work:

• Adopt Reconcile/Delete pattern for virtual machines, scale sets and managed clusters
• remove dependency on Availability Zones Get() within the AzureMachine controller
• stop using a mix of spec + scope in services as input (WIP here)

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Partially addresses #110 and #609

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

NONE

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CecileRobertMichon

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[CecileRobertMichon]

this is temporary to allow removing use of GetterService. In a follow up, virtualMachinesSvc will also become an azure.Service after we remove all Get() calls from the controller (see #110 for more info).

[CecileRobertMichon]

/hold for release

[CecileRobertMichon]

/hold cancel

[k8s-ci-robot]

@CecileRobertMichon: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-cluster-api-provider-azure-apidiff	304e47d	link	/test pull-cluster-api-provider-azure-apidiff

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.

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[CecileRobertMichon]

/assign @devigned @nader-ziada @alexeldeib

[devigned]

lgtm

Always good to see more red than green in a refactor. Definitely looking forward to the refactor containing the IPAddress changes.

[nader-ziada]

/lgtm