Update error funcs for SDKv2

[mboersma]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Updates the ResourceConflict() and ResourceNotFound() error helper funcs to also recognize Azure SDK for Go v2 error types.

Also removes the unused ResourceGroupNotFound() func, does some refactoring to simplify, and adds unit test coverage.

Which issue(s) this PR fixes:

Refs #2974

Special notes for your reviewer:

I extracted this from my larger PR in-progress because it stands on its own. I'll keep trying to do that to keep the pieces reviewable.

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

NONE

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.05% 🎉

Comparison is base (e2a0c6c) 54.77% compared to head (f8323b8) 54.82%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3812      +/-   ##
==========================================
+ Coverage   54.77%   54.82%   +0.05%     
==========================================
  Files         187      187              
  Lines       19098    19099       +1     
==========================================
+ Hits        10460    10471      +11     
+ Misses       8070     8060      -10     
  Partials      568      568              

Files Changed	Coverage Δ
azure/errors.go	28.57% <100.00%> (+19.48%)	⬆️

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[Jont828]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 0ce68ee9dae056755ffc74acda58aa93fb792b8b

[nojnhuh]

/lgtm

[nojnhuh]

/approve

[k8s-ci-robot]

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