Restore instance type sanity check using cluster ami

[ddeidda]

This commit restores the fix for instance type sanity checks using the actual cluster AMI, including new logic to handle the case where the AMIs are still under development.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #2487 (575eedd) into develop (b3dd0ea) will increase coverage by 0.18%.
The diff coverage is 93.75%.

@@             Coverage Diff             @@
##           develop    #2487      +/-   ##
===========================================
+ Coverage    61.85%   62.03%   +0.18%     
===========================================
  Files           40       40              
  Lines         6189     6214      +25     
===========================================
+ Hits          3828     3855      +27     
+ Misses        2361     2359       -2     

Impacted Files	Coverage Δ
cli/src/pcluster/models/hit/hit_cluster_model.py	22.58% <0.00%> (ø)
cli/src/pcluster/models/sit/sit_cluster_model.py	19.35% <0.00%> (ø)
cli/src/pcluster/cluster_model.py	61.81% <100.00%> (+12.40%)	⬆️
cli/src/pcluster/utils.py	67.63% <0.00%> (+0.16%)	⬆️

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