refactor: Make available complete image info, instead of UUID only

[dlipovetsky]

What this PR does / why we need it:
We plan to make decisions based on the complete image info.

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 #

How Has This Been Tested?:

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration and test output

Special notes for your reviewer:

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

Release note:

[thunderboltsid]

trying to fix the failing tests in #490 and #491

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 18 lines in your changes missing coverage. Please review.

Project coverage is 34.70%. Comparing base (fec1de5) to head (1434308).

Files with missing lines	Patch %	Lines
controllers/nutanixmachine_controller.go	0.00%	10 Missing ⚠️
api/v1beta1/nutanix_types.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #489      +/-   ##
==========================================
+ Coverage   33.46%   34.70%   +1.23%     
==========================================
  Files          17       18       +1     
  Lines        2235     2239       +4     
==========================================
+ Hits          748      777      +29     
+ Misses       1467     1442      -25     
  Partials       20       20              

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[dlipovetsky]

I made substantial changes to GetImageByNameOrUUID, and I've created new unit tests for this--there were none before. I made incidental changes to getSystemDisk or getBootstrapDisk, and I'm not convinced I should add unit tests for these in this PR.