feat: mark & hide deprecated operations

[danielgtaylor]

This feature marks operations that are deprecated in OpenAPI as deprecated in the CLI as well, effectively hiding them from the top level --help listing and putting a warning when using them directly by utilizing a built-in cobra feature.

[codecov]

Codecov Report

Merging #138 (3cde380) into main (0d2eae2) will decrease coverage by 0.00%.
The diff coverage is 84.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
- Coverage   64.65%   64.64%   -0.01%     
==========================================
  Files          22       22              
  Lines        2405     2410       +5     
==========================================
+ Hits         1555     1558       +3     
- Misses        685      686       +1     
- Partials      165      166       +1     

Impacted Files	Coverage Δ
openapi/openapi.go	52.48% <50.00%> (-0.04%)	⬇️
cli/operation.go	77.77% <100.00%> (+0.35%)	⬆️

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