chore: deprecate aci-connector addon

[jackfrancis]

Reason for Change:

This PR deprecates the "aci-connector" addon, which has long been unmaintained, and is based on an old version of virtual-kubelet.

virtual-kubelet integrations will work fine on Kubernetes + Azure clusters created w/ aks-engine, and we will leave it to the user to develop those integrations.

Issue Fixed:

Credit Where Due:

Does this change contain code from or inspired by another project?

• No
• Yes

If "Yes," did you notify that project's maintainers and provide attribution?

• No
• Yes

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[jackfrancis]

cc @cpuguy83

[codecov]

Codecov Report

Merging #4276 (37bc2e9) into master (b9c9dda) will decrease coverage by 0.03%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #4276      +/-   ##
==========================================
- Coverage   72.06%   72.02%   -0.04%     
==========================================
  Files         141      141              
  Lines       21686    21650      -36     
==========================================
- Hits        15628    15594      -34     
+ Misses       5107     5106       -1     
+ Partials      951      950       -1     

Impacted Files	Coverage Δ
pkg/api/addons.go	98.05% <ø> (-0.05%)	⬇️
pkg/api/common/const.go	100.00% <ø> (ø)
pkg/api/converterfromapi.go	95.69% <ø> (-0.01%)	⬇️
pkg/api/convertertoapi.go	94.01% <ø> (-0.02%)	⬇️
pkg/api/defaults-custom-cloud-profile.go	85.12% <ø> (-0.13%)	⬇️
pkg/api/k8s_versions.go	100.00% <ø> (ø)
pkg/engine/artifacts.go	98.93% <ø> (-0.03%)	⬇️
pkg/engine/params_k8s.go	79.57% <ø> (-0.56%)	⬇️
pkg/engine/template_generator.go	68.20% <ø> (-0.15%)	⬇️
pkg/engine/templates_generated.go	43.17% <ø> (-0.25%)	⬇️
... and 2 more

---

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[cpuguy83]

LGTM

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

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[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [jackfrancis]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment