ASOAPI: update docs

[nojnhuh]

What type of PR is this?
/kind documentation

What this PR does / why we need it:

This updates the existing docs on the experimental ASOAPI from "this is a thing in-progress" to "this is a thing that's done."

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Part of #4713

Special notes for your reviewer:

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

An experimental ASO-based API for AKS clusters is now available behind the `ASOAPI` feature flag and can be enabled through he `EXP_ASO_API` environment variable when installing CAPZ.

[nojnhuh]

/milestone v1.15

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.77%. Comparing base (7e0ce0c) to head (2e74514).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4802      +/-   ##
==========================================
+ Coverage   62.73%   62.77%   +0.04%     
==========================================
  Files         199      199              
  Lines       16507    16569      +62     
==========================================
+ Hits        10356    10402      +46     
- Misses       5381     5389       +8     
- Partials      770      778       +8     

☔ View full report in Codecov by Sentry.
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[nojnhuh]

/hold for squash

[mboersma]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 5cd63d654039192a02c96f0c68a0bf8971b8d665

[jackfrancis]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis

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• OWNERS [jackfrancis]

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[nojnhuh]

squashed!
/hold cancel